tailcfg: add node attr for SSH environment variables (#13450) #4

Job	Run time
cross (linux, arm64)	6m 4s
cross (linux, 386)	5m 58s
cross (linux, loong64)	6m 2s
cross (linux, arm, 5)	5m 48s
cross (linux, arm, 7)	4m 50s
ios	45s
cross (darwin, amd64)	5m 45s
cross (darwin, arm64)	6m 7s
privileged	55s
cross (windows, amd64)	5m 35s
cross (windows, arm64)	5m 34s
cross (freebsd, amd64)	5m 48s
race-build	4m 20s
race-root-integration (1/4)	1m 19s
cross (openbsd, amd64)	5m 45s
test (amd64, -coverprofile=/tmp/coverage.out)	9m 17s
race-root-integration (2/4)	1m 20s
vm	0s
race-root-integration (3/4)	1m 15s
test (amd64, -race, 1/3)	9m 51s
race-root-integration (4/4)	1m 18s
windows	10m 56s
test (amd64, -race, 2/3)	7m 27s
test (amd64, -race, 3/3)	7m 43s
test (386)	7m 12s
android	54s
crossmin (plan9, amd64)	3m 4s
crossmin (aix, ppc64)	3m 11s
depaware	30s
fuzz	0s
go_generate	1m 6s
licenses	7s
go_mod_tidy	26s
staticcheck (linux, amd64)	3m 26s
tailscale_go	30s
wasm	9m 37s
staticcheck (windows, amd64)	3m 22s
staticcheck (darwin, amd64)	3m 26s
staticcheck (windows, 386)	3m 23s
check_mergeability	1s
notify_slack	7s
	2h 40m 4s

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