Arbos 60: Return back recent WASMs cache

[wurdum]

Should be merged after #890

Closes #879 #421

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.21%. Comparing base (ca5182f) to head (87ff3c2).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #897      +/-   ##
==========================================
+ Coverage   74.90%   75.21%   +0.31%     
==========================================
  Files         243      243              
  Lines       14940    14947       +7     
  Branches     2276     2278       +2     
==========================================
+ Hits        11191    11243      +52     
+ Misses       2892     2844      -48     
- Partials      857      860       +3     

Files with missing lines	Coverage Δ
...thermind.Arbitrum/Arbos/Programs/StylusPrograms.cs	73.50% <100.00%> (+0.62%)	⬆️
src/Nethermind.Arbitrum/Stylus/WasmStore.cs	94.00% <100.00%> (+5.11%)	⬆️

... and 2 files with indirect coverage changes

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[Copilot]

Pull request overview

This PR reintroduces a per-block "recent WASMs" cache that allows the second and subsequent Stylus calls to the same code hash within a block to be charged the cheaper "cached" init gas, gated behind ArbOS v60 (StylusContractLimit) to preserve historical consensus. The previous (broken) ClockCache-based RecentWasms is replaced with an LruCache<ValueHash256, byte>, matching Nitro's post-v60 fix semantics.

Changes:

• Rewrite RecentWasms as a sealed class wrapping a lazily-allocated LruCache, clamping a 0 capacity to 1 to mirror Nitro's lru.NewBasicLRU behavior.
• Gate the Insert(...)-based cached-hit determination in StylusPrograms.CallProgram on ArbosVersion >= StylusContractLimit.
• Add RecentWasmsTests (insert/miss/hit/eviction/zero-capacity/clear) and StylusProgramsTests cases comparing pre-v60 vs v60 same-block vs v60 across-block gas consumption.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/Nethermind.Arbitrum/Stylus/WasmStore.cs	Replaces RecentWasms (ClockCache-based no-op) with an LRU cache that returns hit/miss and supports Clear().
src/Nethermind.Arbitrum/Arbos/Programs/StylusPrograms.cs	Adds the v60 gate around the recent-cache lookup in CallProgram's cached-flag computation.
src/Nethermind.Arbitrum.Test/Stylus/RecentWasmsTests.cs	New unit tests for the LRU semantics of RecentWasms.
src/Nethermind.Arbitrum.Test/Arbos/Programs/StylusProgramsTests.cs	Adds end-to-end gas-charge tests for repeat calls pre-v60, v60 same-block, and v60 across blocks; refactors helpers to be static and version-parameterized.

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[svlachakis]

Maybe worth starting consolidating tests into test cases generally

[wurdum]

Maybe worth starting consolidating tests into test cases generally

Not sure I understand. Could you explain what do you mean?