CLI: enable Wasm custom-page-sizes proposal by default

[Robbepop]

We do not (yet) have CLI options to enable or disable Wasm proposals, so it is more usable to just enable all available ones at the moment so users can try them out.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 70.76%. Comparing base (79170ab) to head (4a05b7b).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/cli/src/context.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1363      +/-   ##
==========================================
- Coverage   70.77%   70.76%   -0.02%     
==========================================
  Files         154      154              
  Lines       14336    14337       +1     
==========================================
- Hits        10146    10145       -1     
- Misses       4190     4192       +2     

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