fix: resolve shadowed modifiers via IdentifierPath

[cats2101]

Summary

Fixes #2838

When a modifier is referenced via IdentifierPath (e.g. A.m in function f() public A.m), the compiler resolves the exact declaration id via referencedDeclaration. However, _find_variable_from_ref_declaration was filtering out matches where is_shadowed is true — which incorrectly rejected parent modifiers that are overridden by a child contract.

Since referencedDeclaration is the compiler's authoritative resolution, we should trust it without filtering by is_shadowed. The shadowed filter is appropriate for name-based lookups (where you want the most-derived version), but not when looking up by compiler-resolved id.

Before

ERROR:ContractSolcParsing:Missing function Variable not found: A.m (context C)

After

Parses correctly, no error.

Reproducer

contract A {
    modifier m() virtual { _; }
}

contract C is A {
    modifier m() override { _; }
    function f() public A.m returns (uint) { return 1; }
}

Test plan

• Verified fix resolves the exact reproducer from [Bug-Candidate]: Slither is unable to locate the Modifier referenced in the IdentifierPath format. #2838
• All 6593 AST parsing tests pass
• All 150 modifier-related parsing tests pass

[CLAassistant]

All committers have signed the CLA.

[cats2101]

Gentle ping — anything else needed here?