Add ergonomic Client class for testing MCP servers #4072

Job	Run time
checks / pre-commit	34s
checks / readme-snippets	11s
checks / test (3.11, lowest-direct, windows-latest)	2m 37s
checks / test (3.12, highest, ubuntu-latest)	53s
checks / test (3.13, lowest-direct, windows-latest)	2m 33s
checks / test (3.11, lowest-direct, ubuntu-latest)	49s
checks / test (3.10, highest, windows-latest)	2m 29s
checks / test (3.14, lowest-direct, windows-latest)	2m 25s
checks / test (3.10, lowest-direct, windows-latest)	2m 27s
checks / test (3.11, highest, ubuntu-latest)	50s
checks / test (3.13, lowest-direct, ubuntu-latest)	44s
checks / test (3.10, lowest-direct, ubuntu-latest)	48s
checks / test (3.14, highest, ubuntu-latest)	1m 10s
checks / test (3.10, highest, ubuntu-latest)	46s
checks / test (3.13, highest, ubuntu-latest)	46s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 11s
checks / test (3.14, highest, windows-latest)	2m 22s
checks / test (3.13, highest, windows-latest)	2m 43s
checks / test (3.11, highest, windows-latest)	2m 34s
checks / test (3.12, lowest-direct, ubuntu-latest)	53s
checks / test (3.12, highest, windows-latest)	4m 26s
checks / test (3.12, lowest-direct, windows-latest)	3m 21s
	37m 32s

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