Enable ruff's literal-membership (PLR6201) rule and fix violations

[weiji14]

Description of proposed changes

Enable ruff's literal membership (PLR6201) rule to ensure a set literal is used when testing for membership. Note that this is a preview mode feature.

This offers a bit of a speed/performance improvement, as Python's peephole optimizer will optimize set membership tests (by converting the set to a frozenset), making it faster than tuple or list membership tests.

Example speed tests on my machine, about a 4.5x speedup using set {} compared to tuple () or list []:

$ python -m timeit -s 'convention="t"' 'convention in {"a", "c", "m", "d", "z", "p", "x", "y", "t"}'
50000000 loops, best of 5: 9.52 nsec per loop

$ python -m timeit -s 'convention="t"' 'convention in ("a", "c", "m", "d", "z", "p", "x", "y", "t")'
5000000 loops, best of 5: 42.4 nsec per loop

$ python -m timeit -s 'convention="t"' 'convention in ["a", "c", "m", "d", "z", "p", "x", "y", "t"]'
5000000 loops, best of 5: 42.4 nsec per loop

References:

• https://docs.python.org/3/whatsnew/3.2.html#optimizations
• https://docs.astral.sh/ruff/rules/literal-membership/
• https://docs.astral.sh/ruff/preview/#selecting-single-preview-rules

Addresses #2741 (comment)

Reminders

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[weiji14]

Note that this change is to fix a PT001 rule violation that was triggered because of the preview mode setting. In non-preview mode, @pytest.fixture() is valid, but in preview mode, @pytest.fixture() is valid. See https://docs.astral.sh/ruff/rules/pytest-fixture-incorrect-parentheses-style/ and astral-sh/ruff#12106.

[seisman]

Three geopandas tests start to fail, but not sure if it's related to changes in this PR.

[weiji14]

Three geopandas tests start to fail, but not sure if it's related to changes in this PR.

Interesting, I can reproduce the geopandas test failures locally, and it seems to be due to the change from () to {} here on this line. Example test failure on pygmt.tests.test_geopandas.test_geopandas_plot_int64_as_float:

baseline (correct)	result (incorrect)	diff

It seems to be because geojson[col].dtype is a class instance like numpy.dtypes.Int64DType rather than a str, and that might be causing some issues with the membership test?

The fix is straightforward though:

Suggested change

	if geojson[col].dtype in {"int", "int64", "Int64"}:
	if geojson[col].dtype.name in {"int", "int64", "Int64"}: