Make wasmi::Module implement Clone

[Robbepop]

This mirrors the fact that Wasmtime's Module is also Clone which is reflected by the standardized Wasm C-API that views Wasm modules as reference types which are generally cheaply clone-able.

Benchmarks conducted locally didn't show any significant performance regressions. There were a few minor 2% perf regressions which could have also been noise.

[codecov]

Codecov Report

Attention: Patch coverage is 81.39535% with 8 lines in your changes missing coverage. Please review.

Project coverage is 80.56%. Comparing base (b957725) to head (68e5506).

Files	Patch %	Lines
crates/wasmi/src/module/mod.rs	81.08%	7 Missing ⚠️
crates/wasmi/src/module/export.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1130      +/-   ##
==========================================
- Coverage   80.56%   80.56%   -0.01%     
==========================================
  Files         273      273              
  Lines       25080    25085       +5     
==========================================
+ Hits        20206    20210       +4     
- Misses       4874     4875       +1     

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