Add CI for 32-bit Linux target & cleanup PR action

[jedel1043]

This PR:

• Adds a new job that tests against i686-unknown-linux-gnu to check that any assumptions we do are also valid for 32-bit targets.
• Cleans up our PR action file to avoid running any build/test jobs if the lint/fmt/typos/docs checks failed.

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	52,963	52,963	0
Passed	49,935	49,935	0
Ignored	2,207	2,207	0
Failed	821	821	0
Panics	0	0	0
Conformance	94.28%	94.28%	0.00%

Tested main commit: ea849b7140574c446fbad07ccb7a7e0a3b85cb17
Tested PR commit: 44a1a74074e76ebe0894f568823a2736910043d8
Compare commits: ea849b7...44a1a74

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.97%. Comparing base (6ddc2b4) to head (44a1a74).
⚠️ Report is 856 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #5090       +/-   ##
===========================================
+ Coverage   47.24%   58.97%   +11.73%     
===========================================
  Files         476      563       +87     
  Lines       46892    62588    +15696     
===========================================
+ Hits        22154    36912    +14758     
- Misses      24738    25676      +938     

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