[ base ] Add non-blocking and timeout variants for channelGet #1155

Job	Run time
initialise	5s
quick-check	5m 31s
macos-bootstrap-chez	9m 18s
nix-bootstrap-chez	6h 0m 13s
ubuntu-bootstrap-racket	12m 19s
ubuntu-bootstrap-chez	6m 38s
ubuntu-self-host-previous-version	10m 27s
windows-bootstrap-chez	23m 57s
ubuntu-build-api	4m 16s
ubuntu-self-host-chez	11m 6s
macos-self-host-chez	19m 30s
ub-test-elab-util	44s
ub-test-collie	20s
ub-pack-test-lsp	15m 39s
ub-pack-test-pack	13m 4s
ub-test-frex	3m 39s
ub-test-katla-and-html	5m 49s
ubuntu-self-host-racket	0s
windows-self-host-racket	11m 35s
	8h 34m 10s

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