test: convert test_integration.py to in-memory transport (fix flaky) … #1520

Job	Run time
checks / pre-commit	32s
checks / readme-snippets	12s
checks / test (3.10, lowest-direct, windows-latest)	2m 27s
checks / test (3.11, lowest-direct, ubuntu-latest)	59s
checks / test (3.10, lowest-direct, ubuntu-latest)	54s
checks / test (3.11, locked, windows-latest)	2m 33s
checks / test (3.12, locked, windows-latest)	2m 58s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 8s
checks / test (3.14, lowest-direct, windows-latest)	2m 28s
checks / test (3.13, lowest-direct, ubuntu-latest)	53s
checks / test (3.14, locked, windows-latest)	2m 54s
checks / test (3.13, locked, ubuntu-latest)	49s
checks / test (3.10, locked, ubuntu-latest)	52s
checks / test (3.14, locked, ubuntu-latest)	2m 10s
checks / test (3.10, locked, windows-latest)	2m 8s
checks / test (3.12, locked, ubuntu-latest)	53s
checks / test (3.13, lowest-direct, windows-latest)	2m 33s
checks / test (3.11, lowest-direct, windows-latest)	2m 22s
checks / test (3.11, locked, ubuntu-latest)	52s
checks / test (3.13, locked, windows-latest)	2m 7s
checks / test (3.12, lowest-direct, windows-latest)	3m 21s
checks / test (3.12, lowest-direct, ubuntu-latest)	58s
all-green	5s
	37m 8s

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