Fix or silence wasmi_wast warnings

[Robbepop]

These warning fixes can be removed once wasmi_wast uses the next version of the wast crate (v220) which includes fixes for these issues: bytecodealliance/wasm-tools#1891

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 81.53%. Comparing base (5b344ca) to head (9059145).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/wast/src/lib.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1288   +/-   ##
=======================================
  Coverage   81.52%   81.53%           
=======================================
  Files         306      306           
  Lines       25277    25275    -2     
=======================================
  Hits        20607    20607           
+ Misses       4670     4668    -2     

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