test: add edge case coverage for Array.prototype.find

[ParthMozarkar]

I added test cases for Array.prototype.find covering edge cases that
weren't tested before:

• Empty array returns undefined
• No match returns undefined
• Returns first match not last
• Works correctly with objects
• Callback receives correct index
• Sparse array holes are visited

No existing tests were removed or modified.

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	52,963	52,963	0
Passed	50,545	50,545	0
Ignored	1,426	1,426	0
Failed	992	992	0
Panics	2	2	0
Conformance	95.43%	95.43%	0.00%

Tested main commit: 0592ecc32629c18d43dc136b6675ef980f37a061
Tested PR commit: 431ba88e8c62ea2eefd85a02539a2014822cad1f
Compare commits: 0592ecc...431ba88

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.79%. Comparing base (6ddc2b4) to head (431ba88).
⚠️ Report is 917 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #5221       +/-   ##
===========================================
+ Coverage   47.24%   59.79%   +12.55%     
===========================================
  Files         476      582      +106     
  Lines       46892    63460    +16568     
===========================================
+ Hits        22154    37948    +15794     
- Misses      24738    25512      +774     

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