Add ergonomic Client class for testing MCP servers #4116

Job	Run time
checks / pre-commit	36s
checks / readme-snippets	11s
checks / test (3.10, lowest-direct, windows-latest)	2m 26s
checks / test (3.10, locked, ubuntu-latest)	50s
checks / test (3.11, locked, windows-latest)	2m 31s
checks / test (3.11, lowest-direct, ubuntu-latest)	47s
checks / test (3.11, lowest-direct, windows-latest)	3m 22s
checks / test (3.10, lowest-direct, ubuntu-latest)	49s
checks / test (3.10, locked, windows-latest)	2m 21s
checks / test (3.12, locked, ubuntu-latest)	47s
checks / test (3.12, lowest-direct, windows-latest)	3m 27s
checks / test (3.14, locked, windows-latest)	3m 2s
checks / test (3.14, lowest-direct, windows-latest)	3m 10s
checks / test (3.11, locked, ubuntu-latest)	48s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 10s
checks / test (3.13, lowest-direct, ubuntu-latest)	43s
checks / test (3.14, locked, ubuntu-latest)	2m 19s
checks / test (3.13, locked, ubuntu-latest)	45s
checks / test (3.13, locked, windows-latest)	2m 52s
checks / test (3.12, locked, windows-latest)	3m 59s
checks / test (3.13, lowest-direct, windows-latest)	2m 24s
checks / test (3.12, lowest-direct, ubuntu-latest)	53s
	40m 12s

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