Implement the Wasm relaxed-simd proposal

[Robbepop]

Closes #1431

Wasmi implements all Wasm relaxed-simd operators in a deterministic way. If possible, it re-uses the non-relaxed versions of the same operators. When compiling with no_std more libm provides soft-float functionality for multiply-add with a single rounding error.

[codecov]

Codecov Report

Attention: Patch coverage is 94.87179% with 6 lines in your changes missing coverage. Please review.

Project coverage is 71.39%. Comparing base (69f1451) to head (effb3f2).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/fuzz/src/config.rs	0.00%	2 Missing ⚠️
crates/wasmi/src/engine/config.rs	33.33%	2 Missing ⚠️
crates/fuzz/src/oracle/wasmi_stack.rs	0.00%	1 Missing ⚠️
crates/fuzz/src/oracle/wasmtime.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1443      +/-   ##
==========================================
+ Coverage   71.21%   71.39%   +0.17%     
==========================================
  Files         161      161              
  Lines       16267    16359      +92     
==========================================
+ Hits        11585    11679      +94     
+ Misses       4682     4680       -2     

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