SpringBoot Tag builds with a toolchainVersion with JDK-${toolchainVersion}

Our Gradle Enterprise conventions automatically tag builds with JDK-${javaVersion} where javaVersion is the version of Java that Gradle is using. Builds using a toolchain set the Toolchain Version custom value but don't apply a JDK tag. To make builds that use a Toolchain easier to find I think we should tag them with JDK-${toolchainVersion} in addition to the existing JDK-${javaVersion} tag.