Add ergonomic Client class for testing MCP servers #4107

Job	Run time
checks / readme-snippets	10s
checks / pre-commit	29s
checks / test (3.11, highest, ubuntu-latest)	44s
checks / test (3.12, lowest-direct, windows-latest)	3m 18s
checks / test (3.11, lowest-direct, ubuntu-latest)	43s
checks / test (3.12, lowest-direct, ubuntu-latest)	51s
checks / test (3.11, lowest-direct, windows-latest)	2m 43s
checks / test (3.10, lowest-direct, windows-latest)	2m 49s
checks / test (3.10, highest, windows-latest)	2m 14s
checks / test (3.12, highest, ubuntu-latest)	54s
checks / test (3.10, lowest-direct, ubuntu-latest)	43s
checks / test (3.12, highest, windows-latest)	3m 22s
checks / test (3.13, highest, windows-latest)	2m 32s
checks / test (3.10, highest, ubuntu-latest)	48s
checks / test (3.14, lowest-direct, windows-latest)	2m 18s
checks / test (3.13, lowest-direct, windows-latest)	3m 33s
checks / test (3.14, highest, windows-latest)	2m 34s
checks / test (3.13, lowest-direct, ubuntu-latest)	43s
checks / test (3.14, highest, ubuntu-latest)	1m 5s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 9s
checks / test (3.13, highest, ubuntu-latest)	42s
checks / test (3.11, highest, windows-latest)	2m 32s
	36m 56s

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