Relocate TestGenerationContext to spring-core-test

This commit moves the test implementation for GenerationContext in
spring-core-test. This also removes the copy we had in testfixtures

See gh-28877

spring-test/src/main/java/org/springframework/test/aot/generate/TestGenerationContext.java

@@ -1,56 +0,0 @@
-/*
- * Copyright 2002-2022 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      https://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.springframework.test.aot.generate;
-
-import org.springframework.aot.generate.ClassNameGenerator;
-import org.springframework.aot.generate.DefaultGenerationContext;
-import org.springframework.aot.generate.GenerationContext;
-import org.springframework.aot.generate.InMemoryGeneratedFiles;
-
-/**
- * {@link GenerationContext} test implementation that uses
- * {@link InMemoryGeneratedFiles}.
- *
- * @author Stephane Nicoll
- * @author Sam Brannen
- * @since 6.0
- */
-public class TestGenerationContext extends DefaultGenerationContext {
-
-	/**
-	 * Create an instance using the specified {@code target}.
-	 * @param target the default target class to use
-	 */
-	public TestGenerationContext(Class<?> target) {
-		this(new ClassNameGenerator(target));
-	}
-
-	/**
-	 * Create an instance using the specified {@link ClassNameGenerator}.
-	 * @param classNameGenerator the class name generator to use
-	 */
-	public TestGenerationContext(ClassNameGenerator classNameGenerator) {
-		super(classNameGenerator, new InMemoryGeneratedFiles());
-	}
-
-
-	@Override
-	public InMemoryGeneratedFiles getGeneratedFiles() {
-		return (InMemoryGeneratedFiles) super.getGeneratedFiles();
-	}
-
-}

spring-test/src/main/java/org/springframework/test/aot/generate/package-info.java

@@ -1,9 +0,0 @@
-/**
- * Test support for core AOT classes.
- */
-@NonNullApi
-@NonNullFields
-package org.springframework.test.aot.generate;
-
-import org.springframework.lang.NonNullApi;
-import org.springframework.lang.NonNullFields;