util/ht: add key-value pair iterator support

[thiagomucci]

Your checklist for this pull request

• I've read the guidelines for contributing to this repository.
• I made sure to follow the project's coding style.
• I've documented every RZ_API function and struct this PR changes.
• x] I've added tests that prove my changes are effective (required for changes to RZ_API).
• I've updated the Rizin book with the relevant information (if needed).
• I've used AI tools to generate fully or partially these code changes and I'm sure the changes are not copyrighted by somebody else.

Detailed description

This pull request implements a Key-Value pair iterator for the generic hashtable API (Ht_).
It introduces two new functions to the Doxygen/C template architecture in ht_inc.h:

• Ht_(as_iter_kv): Creates an iterator to traverse both keys and values.
• Ht_(iter_next_kv): Returns the next HT_(Kv) element in the iteration.

This allows developers to iterate over generic hashtables and access both keys and values simultaneously without needing separate lookups.

AI Disclosure: Gemini was used to debugging the Meson/Ninja local environment, and drafting the unit tests.

Test plan
I have created a dedicated unit test test_ht_uu_iter_kv inside test/unit/test_ht.c. The test populates an HtUU table, initializes the new KV iterator, and asserts that all pairs are traversed correctly.

Test plan
To run and verify the test, i execute:
meson compile -C build
meson test -C build --suite util

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Closing issues

Closes #6426

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[codecov]

Codecov Report

❌ Patch coverage is 72.22222% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 49.29%. Comparing base (d723950) to head (08de586).
⚠️ Report is 8 commits behind head on dev.

Files with missing lines	Patch %	Lines
librz/util/ht/ht_inc.c	72.22%	1 Missing and 4 partials ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
librz/include/rz_util/ht_inc.h	100.00% <ø> (ø)
librz/util/ht/ht_inc.c	76.22% <72.22%> (-0.20%)	⬇️

... and 36 files with indirect coverage changes

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