Fix handling of local assembly variables in ReferencesResolver

[00guap]

The bug was fixed by modifying the handling of local assembly variables in the ReferencesResolver class.

Here's a breakdown of the changes made:

• A stack of sets was added to track local assembly variables and their scopes.
• In the visit and endVisit methods for Block, the local assembly variables stack is updated to push a new set when entering a block and pop it when leaving a block.
• Now when processing a yul::Identifier, the error reporting for undeclared identifiers with _offset or _slot suffixes is only triggered if the identifier is not found in the current local assembly variables scope.
• When processing a yul::VariableDeclaration, the local assembly variables set for the current scope is updated with the new variable before checking for shadowed declarations.

Two new test cases were added to verify the correct handling of local assembly variables with _offset and _slot suffixes.

This fixes issue #14589

[github-actions]

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