Implement CAP-86 - add host functions for efficient 'sparse' map creation/reads.

[dmkozh]

What

This adds sparse_map_new_from_linear_memory and sparse_map_unpack_to_linear_memory host functions, as well as the native host implementation for their slice-based counterparts.

While working on this, I've noticed that the existing host functions for map creation/packing lack test coverage, so this adds behavior tests both for the old and new functions. The code has also been refactored to minimize duplication between the old/new versions and between the slice/linear memory versions.

Why

Implementation of CAP-86

Known limitations

N/A

[Copilot]

Pull request overview

Implements CAP-86 sparse map construction and unpacking across the common ABI, guest, and host layers, with expanded behavioral tests and updated resource observations.

Changes:

• Adds sparse map slice and linear-memory host functions.
• Refactors dense and sparse map handling into shared implementations.
• Adds map behavior tests and refreshes resource baselines.

Reviewed changes

Copilot reviewed 55 out of 97 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
soroban-simulation/src/test/simulation.rs	Updates simulation resource baselines.
soroban-env-host/src/testutils.rs	Adds configurable map Wasm fixtures.
soroban-env-host/src/test/stellar_asset_contract.rs	Updates instruction baseline.
soroban-env-host/src/test/map.rs	Adds dense and sparse map tests.
soroban-env-host/src/test/lifecycle.rs	Updates instruction baseline.
soroban-env-host/src/test/auth.rs	Updates authorization baselines.
soroban-env-host/src/host/mem_helper.rs	Extracts slice scanning and symbol comparison.
soroban-env-host/src/host/data_helper.rs	Implements shared map operations.
soroban-env-host/src/host.rs	Routes map APIs through shared implementations.
soroban-env-host/observations/test__stellar_asset_contract__test_cannot_burn_native.json	Refreshes CPU observations.
soroban-env-host/observations/test__stellar_asset_contract__test_auth_rejected_for_bad_signature_type.json	Refreshes CPU observations.
soroban-env-host/observations/test__stellar_asset_contract__cap_73__test_xlm_transfer_muxed_creates_account.json	Refreshes CPU observations.
soroban-env-host/observations/test__stellar_asset_contract__cap_73__test_xlm_transfer_fails_below_minimum.json	Refreshes CPU observations.
soroban-env-host/observations/test__stellar_asset_contract__cap_73__test_xlm_transfer_creates_account.json	Refreshes CPU observations.
soroban-env-host/observations/test__stellar_asset_contract__cap_73__test_trust_noop_if_trustline_exists.json	Refreshes CPU observations.
soroban-env-host/observations/test__stellar_asset_contract__cap_73__test_trust_noop_for_contract_address.json	Refreshes CPU observations.
soroban-env-host/observations/test__stellar_asset_contract__cap_73__test_trust_fails_for_issuer.json	Refreshes CPU observations.
soroban-env-host/observations/test__stellar_asset_contract__cap_73__test_trust_fails_account_missing.json	Refreshes CPU observations.
soroban-env-host/observations/test__map__sparse_map_unpack_to_slice.json	Records sparse slice unpacking.
soroban-env-host/observations/test__map__sparse_map_unpack_to_linear_memory_roundtrip.json	Records sparse memory roundtrip.
soroban-env-host/observations/test__map__sparse_map_new_from_slices.json	Records sparse slice creation.
soroban-env-host/observations/test__map__sparse_map_new_from_linear_memory_skips_void.json	Records void filtering.
soroban-env-host/observations/test__map__map_new_and_unpack__test_sparse_map_unpack_to_slice.json	Records sparse unpack tests.
soroban-env-host/observations/test__map__map_new_and_unpack__test_sparse_map_new_from_slices.json	Records sparse creation tests.
soroban-env-host/observations/test__map__map_new_and_unpack__test_map_unpack_to_slice.json	Records dense unpack tests.
soroban-env-host/observations/test__map__map_new_and_unpack__test_map_new_from_slices.json	Records dense creation tests.
soroban-env-host/observations/test__map__map_build_bad_element_integrity.json	Updates integrity-error traces.
soroban-env-host/observations/test__map__linear_memory_operations.json	Updates memory-operation costs.
soroban-env-host/observations/test__map__instantiate_oversized_map_from_linear_memory.json	Updates oversized-map observations.
soroban-env-host/observations/test__map__initialization_invalid.json	Updates invalid-input traces.
soroban-env-host/observations/test__linear_memory__test_calling_map_unpack_to_linear_memory_with_pos_out_of_range.json	Updates bounds-error cost.
soroban-env-host/observations/test__linear_memory__test_calling_map_unpack_to_linear_memory_with_length_too_long.json	Updates bounds-error trace.
soroban-env-host/observations/test__linear_memory__test_calling_map_unpack_to_linear_memory_with_good_val_data_ok.json	Updates successful unpack cost.
soroban-env-host/observations/test__linear_memory__test_calling_map_unpack_to_linear_memory_with_good_slices_ok.json	Updates successful slice cost.
soroban-env-host/observations/test__linear_memory__test_calling_map_unpack_to_linear_memory_with_bad_key_ptr.json	Updates bad-pointer cost.
soroban-env-host/observations/test__linear_memory__test_calling_map_unpack_to_linear_memory_with_bad_key_length.json	Updates bad-length cost.
soroban-env-host/observations/test__linear_memory__test_calling_map_new_from_linear_memory_with_invalid_vals.json	Updates invalid-value cost.
soroban-env-host/observations/test__dispatch__invalid_object_handle_sparse_map_unpack_to_linear_memory_arg_0.json	Adds sparse dispatch validation.
soroban-env-guest/src/guest.rs	Adds guest sparse slice adapters.
soroban-env-common/src/symbol.rs	Adds identity Symbol conversion.
soroban-env-common/src/env.rs	Exposes native sparse map APIs.
soroban-env-common/env.json	Defines protocol-28 host functions.

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