Add workflow.instance() API for obtaining current workflow instance #1574

Job	Run time
build-lint-test (3.9, ubuntu-latest)	12m 53s
build-lint-test (3.9, ubuntu-arm)	10m 8s
build-lint-test (3.9, macos-intel)	10m 16s
build-lint-test (3.9, macos-arm)	5m 38s
build-lint-test (3.9, windows-latest)	10m 51s
build-lint-test (3.13, ubuntu-latest)	11m 37s
build-lint-test (3.13, ubuntu-arm)	10m 26s
build-lint-test (3.13, macos-intel)	22m 49s
build-lint-test (3.13, macos-arm)	5m 48s
build-lint-test (3.13, windows-latest)	14m 28s
features-tests / test	5m 42s
	2h 0m 36s

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