Add convenience methods to extract ORM plane blocks

[HarshRajSinghania]

Summary

Adds four convenience methods on OrbitResponseMatrix to extract the plane-specific blocks of the latest orbit response matrix measurement:

• get_h2h_matrix()
• get_v2v_matrix()
• get_h2v_matrix()
• get_v2h_matrix()

Motivation

Addresses #486. The ORM measurement stores the full matrix and plane metadata in latest_measurement (returned by get()). Users currently need to manually slice this matrix using the plane lists. These methods provide a direct, readable way to obtain the four standard blocks (horizontal-to-horizontal, vertical-to-vertical, and the two cross terms).

Implementation

A private _get_submatrix helper selects rows and columns according to the observable and variable plane labels stored with the measurement. The public methods simply call it with the appropriate plane pairs. If no measurement is available the methods return an empty list.

Testing

• Added test_orm_block_getters in tests/tuning_tools/test_tuning_orm.py that performs a small ORM measurement and asserts the expected shapes of each block.
• Ran pytest tests/tuning_tools/test_tuning_orm.py::test_orm_block_getters — passed.
• Ran ruff check and ruff format on the changed files — clean.

Fixes #486