Add ergonomic Client class for testing MCP servers #4113

Job	Run time
checks / pre-commit	35s
checks / readme-snippets	12s
checks / test (3.10, locked, windows-latest)	2m 22s
checks / test (3.11, locked, ubuntu-latest)	43s
checks / test (3.11, lowest-direct, ubuntu-latest)	47s
checks / test (3.12, lowest-direct, ubuntu-latest)	54s
checks / test (3.10, lowest-direct, windows-latest)	2m 59s
checks / test (3.13, lowest-direct, windows-latest)	2m 50s
checks / test (3.10, locked, ubuntu-latest)	44s
checks / test (3.11, lowest-direct, windows-latest)	2m 35s
checks / test (3.12, lowest-direct, windows-latest)	3m 21s
checks / test (3.11, locked, windows-latest)	2m 57s
checks / test (3.12, locked, ubuntu-latest)	50s
checks / test (3.12, locked, windows-latest)	3m 22s
checks / test (3.13, locked, ubuntu-latest)	47s
checks / test (3.10, lowest-direct, ubuntu-latest)	50s
checks / test (3.14, lowest-direct, windows-latest)	3m 2s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 14s
checks / test (3.14, locked, ubuntu-latest)	2m 21s
checks / test (3.13, locked, windows-latest)	2m 12s
checks / test (3.14, locked, windows-latest)	3m 15s
checks / test (3.13, lowest-direct, ubuntu-latest)	44s
	39m 36s

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