feat: add LLVM IR codegen for StructDefStmt and tests

[m-akhil-reddy]

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Pull Request description

#143

How to test these changes

• ...

Pull Request checklists

This PR is a:

• bug-fix
• new feature
• maintenance

About this PR:

• it includes tests.
• the tests are executed on CI.
• the tests generate log file(s) (path).
• pre-commit hooks were executed locally.
• this PR requires a project documentation update.

Author's checklist:

• I have reviewed the changes and it contains no misspelling.
• The code is well commented, especially in the parts that contain more
  complexity.
• New and old tests passed locally.

Additional information

Reviewer's checklist

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## Reviewer's Checklist

- [ ] I managed to reproduce the problem locally from the `main` branch
- [ ] I managed to test the new changes locally
- [ ] I confirm that the issues mentioned were fixed/resolved .

[yuvimittal]

@m-akhil-reddy , i thought you were working on @omsherikar branch, wasnt it? or this is the branch you both will be working on with, so i can close one PR

[m-akhil-reddy]

@yuvimittal , i am wrking in the new branch. i think you can close the other PR.

[m-akhil-reddy]

Hi @yuvimittal , i have made PR for the issue #143 and can please review it , suggest me any changes if needed.

Approach :-

• Added support for translating astx.StructDefStmt into an LLVM identified struct type.
• Introduced two structures in LLVMLiteIRVisitor:
  struct_types – stores created LLVM identified struct types.
  struct_defs – stores struct definitions from the AST.
• Implemented a visit(self, node: astx.StructDefStmt) method to:
  create an LLVM identified struct type for the struct name
  translate attribute types from AST types to LLVM types
  set the struct body with the translated field types
  store the struct type for later use during code generation

Testing :-

• Added a new test: tests/test_struct_definition.py.
• The test defines a struct:-
  struct Point { x: int32, y: int32 }
• The struct definition is included in a simple program with a main function returning 0.
• The test verifies that the module builds successfully and that the struct definition does not break execution.

[yuvimittal]

@m-akhil-reddy , can we have one more test or it will reduce test coverage, rest looks good to me, good work!

[m-akhil-reddy]

@yuvimittal , Thank you for the feedback.

I have added an additional test case for a struct with a single field to improve test coverage.
I also rebased the branch on the latest main to keep the history clean.

Could you please review the changes and if you accept it then i can work on #152 #159 issues.