fix(cli)!: protect client Logger and refactor cli scaletest tests (#8317)

- (breaking) Protects Logger and LogBodies fields of codersdk.Client with its mutex. This addresses a data race in cli/scaletest.
- Fillets the existing cli/createworkspaces unit test and moves the testing logic there into the tests under scaletest/createworkspaces.
- Adds testutil.RaceEnabled bool const and conditionaly skips previously-skipped tests under scaletest/ if the race detector is enabled. This is unfortunate and sad, but I would prefer to have these tests at least running without the race detector than not running at all.
- Adds IgnoreErrors option to fake in-memory agent loggers; having the agents fail the test immediately when they encounter any sort of error isn't really helpful.

testutil/race.go

@@ -0,0 +1,10 @@
+package testutil
+
+// RaceEnabled returns whether the race detector is enabled.
+// This is a constant at compile time. It should be used to
+// conditionally skip tests that are known to be sensitive to
+// being run with the race detector enabled.
+// Please use sparingly and as a last resort.
+func RaceEnabled() bool {
+	return raceEnabled
+}

testutil/race_off.go

@@ -0,0 +1,7 @@
+//go:build !race
+
+package testutil
+
+const (
+	raceEnabled = false
+)

testutil/race_on.go

@@ -0,0 +1,7 @@
+//go:build race
+
+package testutil
+
+const (
+	raceEnabled = true
+)