feat: add support for LiteralDate in LLVM IR builder

[Pratyushanand26]

This PR adds support for LiteralDate handling and its IR translation in the LLVM builder.
Implements new tests under tests/test_literal_date.py to validate both valid and invalid date formats.

Fixes/Implements:

Solve #108

Implements LiteralDate parsing

Adds related LLVM IR translation

Adds validation and error handling for invalid formats

Changed the initialize function as earlier one was deprecated and didn't work

How to test these changes

Activate the conda environment:

conda activate irx

Run the tests:

pytest tests/test_literal_date.py -v

[github-actions]

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src/irx/builders/llvmliteir.py

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tests/test_literal_date.py

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