Configure context on SizeAndTimeBasedRollingPolicy

Previously, when file-based logging was enabled, Logback would output
the following during logging system initialization:

LOGBACK: No context given for c.q.l.core.rolling.SizeAndTimeBasedRollingPolicy

This commit updates the default logback configuration to set the
context on the SizeAndTimeBasedRollingPolicy that it creates.

Fixes gh-21056

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/logging/logback/DefaultLogbackConfiguration.java

 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -139,6 +139,7 @@ class DefaultLogbackConfiguration {
 	private void setRollingPolicy(RollingFileAppender<ILoggingEvent> appender, LogbackConfigurator config,
 			String logFile) {
 		SizeAndTimeBasedRollingPolicy<ILoggingEvent> rollingPolicy = new SizeAndTimeBasedRollingPolicy<>();
+		rollingPolicy.setContext(config.getContext());
 		rollingPolicy.setCleanHistoryOnStart(
 				this.patterns.getProperty("logging.file.clean-history-on-start", Boolean.class, false));
 		rollingPolicy.setFileNamePattern(

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/logging/logback/LogbackLoggingSystemTests.java

 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -111,6 +111,7 @@ class LogbackLoggingSystemTests extends AbstractLoggingSystemTests {
 		this.loggingSystem.initialize(this.initializationContext, null, getLogFile(null, tmpDir()));
 		this.logger.info("Hello world");
 		File file = new File(tmpDir() + "/spring.log");
+		assertThat(output).doesNotContain("LOGBACK:");
 		assertThat(output).contains("Hello world").doesNotContain("Hidden");
 		assertThat(getLineWithText(output, "Hello world")).contains("INFO");
 		assertThat(file.exists()).isTrue();