Expose lsp-bash-allowed-shell and improve warning #5665

Job	Run time
test (ubuntu-latest, 27.2, false)	2m 20s
test (ubuntu-latest, 28.2, false)	2m 44s
test (ubuntu-latest, 29.4, false)	2m 37s
test (macos-latest, 28.2, false)	4m 56s
test (macos-latest, 29.4, false)	4m 7s
test (windows-latest, 27.2, false)	2m 28s
test (windows-latest, 28.2, false)	3m 19s
test (windows-latest, 29.4, false)	3m 24s
test (ubuntu-latest, snapshot, true)	1m 3s
test (macos-latest, snapshot, true)	2m 9s
test (windows-latest, snapshot, true)	2m 30s
	31m 37s

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