pygmt.binstats: Let the parameter 'statistic' support descriptive arguments

[seisman]

Description of proposed changes

Refactor using the new alias system to make the parameter statistic support long-form arguments like statistic="mean" instead of statistic="a".

Upstream documentation at https://docs.generic-mapping-tools.org/dev/gmtbinstats.html

Long-form arguments come from https://github.com/GenericMappingTools/gmt/blob/0ae77bb0ae34d6dcb331156d7ee17a747ba83c57/src/longopt/gmtbinstats_inc.h#L29

Preview: https://pygmt-dev--3012.org.readthedocs.build/en/3012/api/generated/pygmt.binstats.html

Address #1651.

[Copilot]

Pull Request Overview

This PR refactors the pygmt.binstats function to support long-form arguments for the statistic parameter, replacing short single-letter codes with descriptive names (e.g., statistic="mean" instead of statistic="a").

Key changes:

• Implemented an alias system to map long-form statistic names to their corresponding short-form GMT codes
• Added type hints and explicit parameter definitions for better API usability
• Updated tests to use the new long-form syntax

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
pygmt/src/binstats.py	Adds alias system, type hints, and long-form parameter support for statistic names
pygmt/tests/test_binstats.py	Updates existing tests to use long-form statistic names and adds new quantile test