Add ergonomic Client class for testing MCP servers #4109

Job	Run time
checks / pre-commit	31s
checks / readme-snippets	13s
checks / test (3.10, highest, windows-latest)	2m 23s
checks / test (3.12, highest, ubuntu-latest)	54s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 12s
checks / test (3.12, lowest-direct, ubuntu-latest)	51s
checks / test (3.10, lowest-direct, windows-latest)	2m 28s
checks / test (3.11, highest, ubuntu-latest)	50s
checks / test (3.11, lowest-direct, windows-latest)	2m 30s
checks / test (3.12, lowest-direct, windows-latest)	3m 32s
checks / test (3.14, highest, windows-latest)	2m 35s
checks / test (3.10, lowest-direct, ubuntu-latest)	51s
checks / test (3.11, highest, windows-latest)	2m 31s
checks / test (3.10, highest, ubuntu-latest)	48s
checks / test (3.13, highest, ubuntu-latest)	46s
checks / test (3.13, highest, windows-latest)	2m 59s
checks / test (3.11, lowest-direct, ubuntu-latest)	48s
checks / test (3.13, lowest-direct, ubuntu-latest)	47s
checks / test (3.14, lowest-direct, windows-latest)	2m 12s
checks / test (3.12, highest, windows-latest)	3m 46s
checks / test (3.14, highest, ubuntu-latest)	1m 14s
checks / test (3.13, lowest-direct, windows-latest)	2m 36s
	37m 17s

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