fix: assert handle weight and refactor handle

[MrCroxx]

Signed-off-by: MrCroxx mrcroxx@outlook.com## 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 title. Also rename charge to weight.

Checklist

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

Related issues or PRs (optional)

close #338

[codecov]

Codecov Report

Attention: Patch coverage is 92.30769% with 8 lines in your changes are missing coverage. Please review.

Project coverage is 78.10%. Comparing base (cbedab1) to head (cae4c3b).

Files	Patch %	Lines
foyer-memory/src/cache.rs	0.00%	5 Missing ⚠️
foyer-memory/src/generic.rs	87.50%	2 Missing ⚠️
foyer-memory/src/eviction/lru.rs	95.23%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #380      +/-   ##
==========================================
- Coverage   78.13%   78.10%   -0.04%     
==========================================
  Files          51       51              
  Lines        6412     6402      -10     
==========================================
- Hits         5010     5000      -10     
  Misses       1402     1402              

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