Call operator type specifying extensions for bitwise and arithmetic operators

[Firehed]

Summary

This PR ensures OperatorTypeSpecifyingExtension implementations are called consistently for all supported binary operators:

• Add extension calls to getBitwiseAndType, getBitwiseOrType, getBitwiseXorType
• Move extension call to the top of resolveCommonMath (before integer range optimization)
• Remove the duplicate extension call that was later in resolveCommonMath

This is prerequisite work for phpstan/phpstan#14288 (GMP operator type inference), split out per review feedback on #5223.

Testing approach

Per @ondrejmirtes' feedback:

"Please introduce the changes to InitializerExprTypeResolver in a separate PR - this will force you to create synthetic extensions just for test purposes... Without this, if we once removed the GMP extensions then this feature would become untested."

This PR creates synthetic test extensions independent of any specific type (like GMP):

1. TestBitwiseOperand - A dummy fixture class
2. TestBitwiseOperatorTypeSpecifyingExtension - Returns TestBitwiseOperand for &, |, ^ operators
3. Uses existing TestDecimal + TestDecimalOperatorTypeSpecifyingExtension for arithmetic operators

The test verifies the resolver correctly invokes extensions for both bitwise and arithmetic operators. This ensures the resolver infrastructure remains tested even if specific extensions (like a future GMP extension) are removed.

Test plan

• Added OperatorTypeSpecifyingExtensionTypeInferenceTest with 8 assertions
• All existing tests pass (11634 tests, 78899 assertions)

Generated with Claude Code

[Firehed]

I believe the two failing tests are unrelated to this change based on other PRs I'm seeing and their associated error messages.