Threading support for the `rp2040` platform #1702

Job	Run time
check-diff / check	21s
lsp / test-lsp (ubuntu-latest)	11m 46s
lsp / test-lsp (macos-latest)	10m 31s
building / build-toolchain (ubuntu-latest)	8m 39s
lsp / test-lsp (windows-latest)	29m 44s
building / build-toolchain (macos-latest)	10m 35s
cli / test-cli (ubuntu-latest)	4m 45s
building / build-toolchain (windows-latest)	13m 51s
cli / test-cli (macos-latest)	7m 38s
cli / test-cli (windows-latest)	7m 27s
building / epoch / build-epoch	11m 37s
	1h 56m 54s

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