Fix bug in JsString ends_with

[nekevss]

This PR closes #5390

Looks like we're calling the wrong method in ends_with. Fixes the issue and adds a basic test for starts_with and ends_with

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	53,125	53,125	0
Passed	51,072	51,072	0
Ignored	1,482	1,482	0
Failed	571	571	0
Panics	0	0	0
Conformance	96.14%	96.14%	0.00%

Tested main commit: 85272bf9c8d17c2609aaeb06f3dee88e7f865e77
Tested PR commit: 28aeba4b0a4bbdc6a03cda44144fdfde007eaf14
Compare commits: 85272bf...28aeba4

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.16%. Comparing base (6ddc2b4) to head (28aeba4).
⚠️ Report is 973 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #5391       +/-   ##
===========================================
+ Coverage   47.24%   60.16%   +12.91%     
===========================================
  Files         476      566       +90     
  Lines       46892    63030    +16138     
===========================================
+ Hits        22154    37921    +15767     
- Misses      24738    25109      +371     

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[hansl]

No test262 changes, uh.