feat: add input parameter validation to PlasmodiumDataResource public methods

[suhaan-24]

Summary

This PR adds basic input parameter validation to the public methods in PlasmodiumDataResource, bringing it in line with the validation patterns already used in the Anopheles API.

Why this matters

Currently, methods like genome_sequence() and variant_calls() accept any input type without validation. When a user passes an invalid parameter (e.g., an incorrect contig string, or a string where a boolean is expected), the error propagates downwards and results in confusing low-level exceptions (like a cryptic zarr KeyError or dask TypeError) instead of a helpful message at the API boundary. This change improves the developer experience by catching these errors early.

Changes

• Added isinstance and type checks to the top of variant_calls() (extended, inline_array, chunks) and genome_sequence() (region, inline_array, chunks) in malariagen_data/plasmodium.py.
• Added 5 new tests to tests/test_plasmodium.py to verify that helpful TypeError and ValueError exceptions are raised for invalid inputs.

Verification

All 32 tests in test_plasmodium.py pass successfully, and there are no changes to the behaviour for valid inputs.
Test Results:

Closes #1022

[suhaan-24]

@jonbrenas Please take a look at it