Propagate contextvars through anyio streams #807

Job	Run time
checks / readme-snippets	12s
checks / pre-commit	31s
checks / test (3.10, locked, ubuntu-latest)	51s
checks / test (3.11, lowest-direct, windows-latest)	2m 33s
checks / test (3.10, locked, windows-latest)	2m 48s
checks / test (3.11, lowest-direct, ubuntu-latest)	51s
checks / test (3.11, locked, ubuntu-latest)	51s
checks / test (3.10, lowest-direct, ubuntu-latest)	58s
checks / test (3.12, lowest-direct, windows-latest)	3m 31s
checks / test (3.12, lowest-direct, ubuntu-latest)	58s
checks / test (3.12, locked, windows-latest)	4m 4s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 15s
checks / test (3.12, locked, ubuntu-latest)	59s
checks / test (3.13, lowest-direct, ubuntu-latest)	53s
checks / test (3.10, lowest-direct, windows-latest)	2m 32s
checks / test (3.14, locked, windows-latest)	3m 3s
checks / test (3.13, lowest-direct, windows-latest)	2m 49s
checks / test (3.13, locked, ubuntu-latest)	49s
checks / test (3.14, locked, ubuntu-latest)	2m 19s
checks / test (3.14, lowest-direct, windows-latest)	2m 26s
checks / test (3.11, locked, windows-latest)	2m 24s
checks / test (3.13, locked, windows-latest)	2m 18s
all-green	3s
	39m 58s

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