[GLib] Rename run-end encoded array values accessor to physical_values #51479

Describe the enhancement requested

As requested in the review of #51276, track the GLib naming change separately:

• Rename the run-end encoded array values property to physical_values (GObject property spelling physical-values).
• Add garrow_run_end_encoded_array_get_physical_values() and deprecate garrow_run_end_encoded_array_get_values() in its favor, preserving the existing accessor for compatibility.
• Update introspection documentation and tests for the physical child accessor.

The existing property exposes the physical values of the runs. In Ruby, its generated getter shadows Array#values, which is intended to return logical Ruby values. Explicit physical naming separates these meanings; #51276 keeps its Ruby conversion work separate from this GLib API change.

Component(s)

GLib, Ruby

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