Add list plugins method and tests #720

Job	Run time
initial_checks / Load tox environments	10s
initial_checks / codestyle (ubuntu-latest)	21s
tests / Load tox environments	7s
tests / py38-test-lts-all (ubuntu-latest)	1m 47s
tests / py39-test (ubuntu-latest)	1m 47s
tests / py310-test-all (ubuntu-latest)	1m 46s
tests / py311-test (ubuntu-latest)	1m 35s
tests / py312-test-all (ubuntu-latest)	2m 14s
tests / py38-docs (ubuntu-latest)	4m 10s
tests / py311-docs (macos-latest)	1m 54s
tests / py38-test-all (macos-12)	2m 10s
tests / py39-test (macos-12)	2m 51s
tests / py310-test-all (macos-latest)	1m 25s
tests / py311-test (macos-latest)	1m 39s
tests / py312-test-all (macos-latest)	2m 46s
tests / py38-test (windows-latest)	2m 58s
tests / py39-test (windows-latest)	2m 56s
tests / py310-test-dev-all (ubuntu-latest)	2m 8s
tests / py311-test-dev (ubuntu-latest)	2m 19s
tests / py312-test-dev-all (ubuntu-latest)	3m 1s
tests / py311-test-dev-all (macos-latest)	1m 55s
tests / py312-test-dev (macos-latest)	3m 47s
tests / py310-test-dev (windows-latest)	3m 20s
publish	0s
	49m 6s

Provide feedback