Make the per-version wire packages private (`mcp_types._v*`) #3693

Job	Run time
checks / readme-snippets	12s
checks / docs	45s
checks / pre-commit	48s
checks / test (3.10, lowest-direct, windows-latest)	1m 54s
checks / test (3.12, locked, windows-latest)	2m 3s
checks / test (3.11, locked, windows-latest)	2m 2s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 23s
checks / test (3.10, locked, windows-latest)	1m 48s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 24s
checks / test (3.12, lowest-direct, windows-latest)	1m 50s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 22s
checks / test (3.11, lowest-direct, windows-latest)	2m 2s
checks / test (3.11, locked, ubuntu-latest)	1m 29s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 23s
checks / test (3.12, locked, ubuntu-latest)	1m 31s
checks / test (3.10, locked, ubuntu-latest)	1m 33s
checks / test (3.14, lowest-direct, windows-latest)	1m 53s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 19s
checks / test (3.13, lowest-direct, windows-latest)	2m 0s
checks / test (3.13, locked, ubuntu-latest)	1m 15s
checks / test (3.14, locked, ubuntu-latest)	1m 20s
checks / test (3.13, locked, windows-latest)	2m 9s
checks / test (3.14, locked, windows-latest)	2m 9s
all-green	5s
	35m 39s

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