Revert "Rework BootRun so that it does not subclass JavaExec"

This reverts commit 6eee9de3c1.

Closes gh-10872

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/resources/org/springframework/boot/gradle/tasks/run/BootRunIntegrationTests-applicationPluginMainClassNameIsNotUsedWhenItIsNull.gradle

@@ -10,6 +10,6 @@ apply plugin: 'org.springframework.boot'
 task echoMainClassName {
 	dependsOn compileJava
 	doLast {
-		println 'Main class name = ' + bootRun.mainClassName
+		println 'Main class name = ' + bootRun.main
 	}
 }

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/resources/org/springframework/boot/gradle/tasks/run/BootRunIntegrationTests-applicationPluginMainClassNameIsUsed.gradle

@@ -10,5 +10,5 @@ apply plugin: 'org.springframework.boot'
 mainClassName = 'com.example.CustomMainClass'
 
 task echoMainClassName {
-	println 'Main class name = ' + bootRun.mainClassName
+	println 'Main class name = ' + bootRun.main
 }

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/resources/org/springframework/boot/gradle/tasks/run/BootRunIntegrationTests-argsCanBeConfigured.gradle

@@ -1,12 +0,0 @@
-buildscript {
-	dependencies {
-		classpath files(pluginClasspath.split(','))
-	}
-}
-
-apply plugin: 'java'
-apply plugin: 'org.springframework.boot'
-
-bootRun {
-	args = ['--com.example.foo=bar']
-}

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/resources/org/springframework/boot/gradle/tasks/run/BootRunIntegrationTests-execSpecCanBeConfigured.gradle

@@ -1,15 +0,0 @@
-buildscript {
-	dependencies {
-		classpath files(pluginClasspath.split(','))
-	}
-}
-
-apply plugin: 'java'
-apply plugin: 'org.springframework.boot'
-
-
-bootRun {
-	execSpec {
-		systemProperty 'com.example.foo', 'bar'
-	}
-}

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/resources/org/springframework/boot/gradle/tasks/run/BootRunIntegrationTests-jvmArgsCanBeConfigured.gradle

@@ -1,12 +0,0 @@
-buildscript {
-	dependencies {
-		classpath files(pluginClasspath.split(','))
-	}
-}
-
-apply plugin: 'java'
-apply plugin: 'org.springframework.boot'
-
-bootRun {
-	jvmArgs = ['-Dcom.example.foo=bar']
-}

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/resources/org/springframework/boot/gradle/tasks/run/BootRunIntegrationTests-springBootExtensionMainClassNameIsUsed.gradle

@@ -12,5 +12,5 @@ springBoot {
 }
 
 task echoMainClassName {
-	println 'Main class name = ' + bootRun.mainClassName
+	println 'Main class name = ' + bootRun.main
 }