test: Improve test coverage for tecDIR_FULL error in xrpld

[neti-soft-com]

High Level Overview of Change

The main goal of this PR is to improve test coverage for the xrpld application.

With the recent ability to simulate the tecDIR_FULL error, we can now comprehensively cover all cases where this error is returned. Consequently, this PR modifies production code solely to remove the now-obsolete LCOV_EXCL_LINE comments.

Context of Change

This PR is enabled by the implementation of #5935.
Once completed, it will resolve issue #5969.

Type of Change

• test: - The changes only affect unit tests.

API Impact

• Public API: New feature (new methods and/or new fields)
• Public API: Breaking change (in general, breaking changes should only impact the next api_version)
• libxrpl change (any change that may affect libxrpl or dependents of libxrpl)
• Peer protocol change (must be backward compatible or bump the peer protocol version)

Test Plan

Verification is done by running the automated unit test suite.
Code coverage metrics will reflect the newly covered tecDIR_FULL error branches.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.6%. Comparing base (e2e537b) to head (505a3f0).

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #6862   +/-   ##
=======================================
  Coverage     81.6%   81.6%           
=======================================
  Files         1010    1010           
  Lines        75982   76007   +25     
  Branches      7633    7632    -1     
=======================================
+ Hits         61982   62008   +26     
+ Misses       14000   13999    -1     

Files with missing lines	Coverage Δ
src/libxrpl/ledger/View.cpp	96.6% <100.0%> (+<0.1%)	⬆️
src/libxrpl/ledger/helpers/MPTokenHelpers.cpp	96.1% <100.0%> (+<0.1%)	⬆️
src/libxrpl/ledger/helpers/NFTokenHelpers.cpp	87.1% <100.0%> (+0.1%)	⬆️
src/libxrpl/ledger/helpers/RippleStateHelpers.cpp	92.6% <100.0%> (+0.1%)	⬆️
...c/libxrpl/tx/transactors/account/SignerListSet.cpp	91.9% <100.0%> (+0.1%)	⬆️
src/libxrpl/tx/transactors/bridge/XChainBridge.cpp	91.4% <100.0%> (+<0.1%)	⬆️
src/libxrpl/tx/transactors/check/CheckCreate.cpp	99.1% <100.0%> (+<0.1%)	⬆️
...rc/libxrpl/tx/transactors/delegate/DelegateSet.cpp	100.0% <100.0%> (ø)
src/libxrpl/tx/transactors/dex/OfferCreate.cpp	93.6% <100.0%> (+0.3%)	⬆️
src/libxrpl/tx/transactors/did/DIDSet.cpp	100.0% <100.0%> (ø)
... and 5 more

... and 2 files with indirect coverage changes

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