Restore dependency in `maven-shade-plugin`

Restore `spring-boot-maven-plugin` dependency in `maven-shade-plugin`
starter configuration. Required so that the shade plugin can use
`PropertiesMergingResourceTransformer` if wanted.

Fixes gh-11200

spring-boot-project/spring-boot-starters/spring-boot-starter-parent/pom.xml

@@ -179,6 +179,13 @@
 							</filter>
 						</filters>
 					</configuration>
+					<dependencies>
+						<dependency>
+							<groupId>org.springframework.boot</groupId>
+							<artifactId>spring-boot-maven-plugin</artifactId>
+							<version>${revision}</version>
+						</dependency>
+					</dependencies>
 					<executions>
 						<execution>
 							<phase>package</phase>
@@ -210,7 +217,8 @@
 						</execution>
 					</executions>
 				</plugin>
-				<!--This plugin's configuration is used to store Eclipse m2e settings only. It has no influence on the Maven build itself.-->
+				<!--This plugin's configuration is used to store Eclipse m2e settings
+					only. It has no influence on the Maven build itself. -->
 				<plugin>
 					<groupId>org.eclipse.m2e</groupId>
 					<artifactId>lifecycle-mapping</artifactId>

spring-boot-project/spring-boot-starters/spring-boot-starter-parent/src/main/xslt/post-process-flattened-pom.xsl

@@ -10,6 +10,10 @@
 			<xsl:apply-templates select="@*|node()" />
 		</xsl:copy>
 	</xsl:template>
+	<xsl:template
+		match="/m:project/m:build/m:pluginManagement/m:plugins/m:plugin/m:dependencies/m:dependency/m:version/text()[. = '${revision}']">
+		<xsl:value-of select="/m:project/m:version/text()" />
+	</xsl:template>
 	<xsl:template match="/m:project/m:properties/m:main.basedir" />
 	<xsl:template match="/m:project/m:groupId" />
 	<xsl:template match="/m:project/m:version" />