community[minor],langchain[minor]: Move base classes and reference implementations to core #12257

Job	Run time
Check linting	17s
test-exports / exports-esbuild	18s
test-exports / exports-esm	10s
test-exports / exports-cf	10s
test-exports / exports-cjs	10s
test-exports / exports-vercel	11s
test-exports / exports-vite	11s
test-exports / exports-tsc	18s
	1m 45s

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