refactor: expose internal error for hybrid cache

[MrCroxx]

What's changed and what's your intention?

Please explain IN DETAIL what the changes are in this PR and why they are needed. :D

AS IS

Checklist

• I have written the necessary rustdoc comments
• I have added the necessary unit tests and integration tests
• I have passed cargo x (or cargo x --fast instead if the old tests are not modified) in my local environment.

Related issues or PRs (optional)

close #1059
apache/opendal#6366

[codecov]

Codecov Report

Attention: Patch coverage is 62.50000% with 21 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
foyer/src/hybrid/error.rs	62.85%	13 Missing ⚠️
foyer/src/hybrid/cache.rs	66.66%	5 Missing ⚠️
foyer-memory/src/error.rs	0.00%	3 Missing ⚠️

Files with missing lines	Coverage Δ
foyer-memory/src/cache.rs	77.10% <100.00%> (ø)
foyer-memory/src/raw.rs	90.74% <100.00%> (ø)
foyer/src/hybrid/builder.rs	92.59% <100.00%> (ø)
foyer-memory/src/error.rs	0.00% <0.00%> (ø)
foyer/src/hybrid/cache.rs	84.68% <66.66%> (+0.26%)	⬆️
foyer/src/hybrid/error.rs	62.85% <62.85%> (ø)

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