Optimize Coroutine invocations

KClass instantiation in CoroutinesUtils is suboptimal, and should be
replaced by KTypes#isSubtypeOf checks using pre-instantiated types for
Flow, Mono and Publisher.

This commit impact on performances is significant since a throughput
increase between 2x and 3x has been measured on basic endpoints.

Closes gh-32390

spring-core/src/test/kotlin/org/springframework/core/CoroutinesUtilsTests.kt

@@ -97,6 +97,29 @@ class CoroutinesUtilsTests {
 		Assertions.assertThatIllegalArgumentException().isThrownBy { CoroutinesUtils.invokeSuspendingFunction(method, this, "foo") }
 	}
 
+	@Test
+	fun invokeSuspendingFunctionWithMono() {
+		val method = CoroutinesUtilsTests::class.java.getDeclaredMethod("suspendingFunctionWithMono", Continuation::class.java)
+		val publisher = CoroutinesUtils.invokeSuspendingFunction(method, this)
+		Assertions.assertThat(publisher).isInstanceOf(Mono::class.java)
+		StepVerifier.create(publisher)
+			.expectNext("foo")
+			.expectComplete()
+			.verify()
+	}
+
+	@Test
+	fun invokeSuspendingFunctionWithFlux() {
+		val method = CoroutinesUtilsTests::class.java.getDeclaredMethod("suspendingFunctionWithFlux", Continuation::class.java)
+		val publisher = CoroutinesUtils.invokeSuspendingFunction(method, this)
+		Assertions.assertThat(publisher).isInstanceOf(Flux::class.java)
+		StepVerifier.create(publisher)
+			.expectNext("foo")
+			.expectNext("bar")
+			.expectComplete()
+			.verify()
+	}
+
 	@Test
 	fun invokeSuspendingFunctionWithFlow() {
 		val method = CoroutinesUtilsTests::class.java.getDeclaredMethod("suspendingFunctionWithFlow", Continuation::class.java)
@@ -213,6 +236,16 @@ class CoroutinesUtilsTests {
 		return value
 	}
 
+	suspend fun suspendingFunctionWithMono(): Mono<String> {
+		delay(1)
+		return Mono.just("foo")
+	}
+
+	suspend fun suspendingFunctionWithFlux(): Flux<String> {
+		delay(1)
+		return Flux.just("foo", "bar")
+	}
+
 	suspend fun suspendingFunctionWithFlow(): Flow<String> {
 		delay(1)
 		return flowOf("foo", "bar")