Implement getter for Context.instructions_remaining

[ShovelTime]

This implements Context.instructions_remaining()
for reading the remaining instruction budget of the Context, without the need for pointer arithmetic to access the field otherwise.

​This would be useful for cases where we want to monitor engine usage in a remote service for billing purposes

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	52,862	52,862	0
Passed	49,472	49,471	-1
Ignored	2,249	2,249	0
Failed	1,141	1,142	+1
Panics	0	0	0
Conformance	93.59%	93.59%	-0.00%

Broken tests (1):

test/intl402/NumberFormat/prototype/resolvedOptions/basic.js (previously Passed)

[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.54%. Comparing base (6ddc2b4) to head (4a6bd1f).
⚠️ Report is 678 commits behind head on main.

Files with missing lines	Patch %	Lines
core/engine/src/context/mod.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4624      +/-   ##
==========================================
+ Coverage   47.24%   56.54%   +9.30%     
==========================================
  Files         476      548      +72     
  Lines       46892    60009   +13117     
==========================================
+ Hits        22154    33934   +11780     
- Misses      24738    26075    +1337     

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[jedel1043]

Seems a reasonable enough addition. We might want to have discussions about "lifting" the instructions_remaining parameter out of the fuzz feature, but that can be done in the future.