chore: rm redundant clones

[LesnyRumcajs]

Got rid of some redundant clones here while I was doing the same in Forest.

[Copilot]

Pull request overview

This PR removes a few redundant heap allocations/clones across the SDK and FVM implementation, reducing unnecessary copying while preserving behavior.

Changes:

• Avoid cloning return buffers when constructing IpldBlock responses in the SDK.
• Serialize pieces directly without allocating an intermediate Vec<PieceInfo>.
• Remove redundant PathBuf cloning and avoid TokenAmount cloning in gas cost computation.

Reviewed changes

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

File	Description
sdk/src/lib.rs	Moves the already-owned return buffer into IpldBlock instead of cloning it.
sdk/src/crypto.rs	Serializes the pieces slice directly, avoiding an intermediate allocation.
fvm/src/kernel/default.rs	Passes &PathBuf to create_dir_all instead of cloning the path.
fvm/src/executor/default.rs	Computes gas cost by borrowing gas_fee_cap rather than cloning it.

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 25.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.04%. Comparing base (ef0a993) to head (3266f89).

Files with missing lines	Patch %	Lines
fvm/src/kernel/default.rs	0.00%	1 Missing ⚠️
sdk/src/crypto.rs	0.00%	1 Missing ⚠️
sdk/src/lib.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2325   +/-   ##
=======================================
  Coverage   77.04%   77.04%           
=======================================
  Files         143      143           
  Lines       14203    14203           
=======================================
  Hits        10943    10943           
  Misses       3260     3260           

Files with missing lines	Coverage Δ
fvm/src/executor/default.rs	73.97% <100.00%> (ø)
fvm/src/kernel/default.rs	80.72% <0.00%> (ø)
sdk/src/crypto.rs	0.00% <0.00%> (ø)
sdk/src/lib.rs	0.00% <0.00%> (ø)

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