Coverage library: replace memory-safe-assembly special comment with block annotation

[anaPerezGhiglia]

The Solidity compiler emits a deprecation warning about memory-safe-assembly Natspec when coverage.sol is part of the compilation input.

Warning: Natspec memory-safe-assembly special comment for inline assembly is deprecated and scheduled for removal. Use the memory-safe block annotation instead.
  --> __hardhat_coverage_library_a3e9cfe2-41b4-4a1f-ad9e-ac62dd82979e.sol:11:5:
   |
11 |     assembly {
   |     ^ (Relevant source part starts here and spans across multiple lines).

Even though the snippet still mentions __hardhat_coverage_library (the old HH-hosted library), this also happens for the EDR-hosted library file. Filing the issue in EDR since, after #1363, EDR is responsible for the library file.

[anaPerezGhiglia]

I created the issue in EDR with the idea of replacing the deprecated Natspec comment

/// @solidity memory-safe-assembly
assembly { ... }

with the assembly block annotation as suggested by the warning

assembly ("memory-safe") { ... }

However, the modern and official way is only supported in Solidity 0.8.13 and newer. Is this a blocker for HH users?

Should we take the same approach taken in NomicFoundation/hardhat#7842 for console.sol library? That is, keep the library file unchanged, just filter the warnings on HH side?

@kanej @alcuadrado

[anaPerezGhiglia]

We created NomicFoundation/hardhat#8251 to suppress warnings. We can keep this issue to track the need to change the library to use the suggested assembly block annotation.
We need to make sure that we are good with restricting to Solidity 0.8.13 and newer.

[kanej]

Hey @anaPerezGhiglia, I think that is the right call. Hardhat has to support older version of Solidity, so switching to the new syntax is not an option. Switching based on the solc version in use might be, but that is a bigger task than warning suppression.
We will tackle NomicFoundation/hardhat#8251