feat(irx): add utf8 and large_utf8 string columns to record batch

[yogendra-17]

Pull Request description

This PR adds string columns so IRx record batches can hold text, still fully Arrow-compatible.

What changed

• Added two text column types: UTF8 (normal strings) and LARGE_UTF8 (64-bit offsets, for very large text).
• append_string(...) to write text and get_string(...) to read it back handles any language and emoji (multi-byte UTF-8), empty strings, and null/missing values.
• Wired through all three layers that must agree: the native C++ library (irx_record_batch.cpp/.h), the Python ctypes wrapper (irx/record_batch.py), and the RuntimeFeature symbol table(builder/runtime/record_batch.py) so compiled IRx programs get the symbols too.

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

This is the string half of (string + temporal types), built on the Arrow C++ bridge from #88. Temporal types (date/timestamp) follow in a separate PR to keep this one small and reviewable.

Reviewer's checklist

Copy and paste this template for your review's note:

## 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]

on a null slot this returns an empty view rather than an error. That's consistent with the numeric getters, so no change needed here, but please add a line to the get_string docstring in record_batch.py telling callers to check is_null first.

[yuvimittal]

This tests the append-side type mismatch, but the get-side branch (irx_rb_batch_get_utf8 on a non-string column) is untested, add a case that builds an INT32 batch and asserts get_string raises.

[yuvimittal]

@yogendra-17 , can you please rebase your branch ? The core design is correct, thanks for working on that. I have added some small comments, but we can push them later