Add ergonomic Client class for testing MCP servers #4103

Job	Run time
checks / pre-commit	20s
checks / readme-snippets	10s
checks / test (3.11, lowest-direct, windows-latest)	2m 23s
checks / test (3.11, highest, ubuntu-latest)	45s
checks / test (3.11, lowest-direct, ubuntu-latest)	42s
checks / test (3.10, highest, windows-latest)	2m 25s
checks / test (3.10, lowest-direct, windows-latest)	2m 18s
checks / test (3.10, lowest-direct, ubuntu-latest)	44s
checks / test (3.13, lowest-direct, ubuntu-latest)	43s
checks / test (3.12, highest, windows-latest)	3m 56s
checks / test (3.12, lowest-direct, windows-latest)	3m 22s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 2s
checks / test (3.14, lowest-direct, windows-latest)	2m 9s
checks / test (3.13, highest, windows-latest)	2m 15s
checks / test (3.13, lowest-direct, windows-latest)	2m 22s
checks / test (3.13, highest, ubuntu-latest)	46s
checks / test (3.14, highest, windows-latest)	2m 48s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 10s
checks / test (3.12, highest, ubuntu-latest)	50s
checks / test (3.14, highest, ubuntu-latest)	1m 12s
checks / test (3.10, highest, ubuntu-latest)	45s
checks / test (3.11, highest, windows-latest)	2m 31s
	35m 38s

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