Do not discover annotation processors from the classpath in tests

Previously, if an annotation processors was present in the classpath
it was executed as part of tests using `TestCompiler`.

This commit updates `TestCompiler` to always set the annotation
processors to use. By default, this sets an empty list which does not
use annotation processing.

Closes gh-31791

spring-core-test/src/main/java/org/springframework/core/test/tools/TestCompiler.java

@@ -311,9 +311,7 @@ public final class TestCompiler {
 			Errors errors = new Errors();
 			CompilationTask task = this.compiler.getTask(null, fileManager, errors,
 					this.compilerOptions, null, compilationUnits);
-			if (!this.processors.isEmpty()) {
 			task.setProcessors(this.processors);
-			}
 			boolean result = task.call();
 			if (!result || errors.hasReportedErrors()) {
 				throw new CompilationException(errors.toString(), this.sourceFiles, this.resourceFiles);