fix: set preset parameters in the API rather than the frontend (#17403)

Follow-up from a [previous Pull
Request](https://github.com/coder/coder/pull/16965) required some
additional testing of Presets from the API perspective.

In the process of adding the new tests, I updated the API to enforce
preset parameter values based on the selected preset instead of trusting
whichever frontend makes the request. This avoids errors scenarios in
prebuilds where a prebuild might expect a certain preset but find a
different set of actual parameter values.

coderd/util/slice/slice.go

@@ -66,6 +66,19 @@ func Contains[T comparable](haystack []T, needle T) bool {
 	})
 }
 
+func CountMatchingPairs[A, B any](a []A, b []B, match func(A, B) bool) int {
+	count := 0
+	for _, a := range a {
+		for _, b := range b {
+			if match(a, b) {
+				count++
+				break
+			}
+		}
+	}
+	return count
+}
+
 // Find returns the first element that satisfies the condition.
 func Find[T any](haystack []T, cond func(T) bool) (T, bool) {
 	for _, hay := range haystack {