Add ergonomic Client class for testing MCP servers #4076

Job	Run time
checks / readme-snippets	11s
checks / pre-commit	24s
checks / test (3.11, highest, windows-latest)	3m 58s
checks / test (3.10, highest, ubuntu-latest)	48s
checks / test (3.10, highest, windows-latest)	2m 26s
checks / test (3.10, lowest-direct, ubuntu-latest)	47s
checks / test (3.10, lowest-direct, windows-latest)	2m 27s
checks / test (3.11, highest, ubuntu-latest)	1m 6s
checks / test (3.13, lowest-direct, windows-latest)	2m 55s
checks / test (3.11, lowest-direct, windows-latest)	3m 16s
checks / test (3.12, lowest-direct, windows-latest)	3m 36s
checks / test (3.12, highest, ubuntu-latest)	54s
checks / test (3.11, lowest-direct, ubuntu-latest)	24s
checks / test (3.12, highest, windows-latest)	4m 25s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 12s
checks / test (3.12, lowest-direct, ubuntu-latest)	51s
checks / test (3.14, lowest-direct, windows-latest)	2m 37s
checks / test (3.13, highest, windows-latest)	3m 13s
checks / test (3.13, highest, ubuntu-latest)	44s
checks / test (3.14, highest, ubuntu-latest)	22s
checks / test (3.13, lowest-direct, ubuntu-latest)	46s
checks / test (3.14, highest, windows-latest)	2m 25s
	39m 47s

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