Add built-in Serena MCP support with language service integration and Go configuration options #20661

Job	Run time
lint	36s
build	1m 11s
test	1m 24s
js	37s
bench	32s
Integration: CLI Compile & Poutine	43s
Integration: CLI Logs & Firewall	22s
Integration: CLI MCP Other	38s
Integration: Workflow	43s
Integration: CLI MCP Playwright	2m 1s
fuzz	1m 48s
	10m 35s

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