RFR: JDK-8303476: Add the runtime version in the release file of a JDK image

[Mandy Chung]

`$JAVA_HOME/release` file currently includes `JAVA_VERSION`  which is the version 
number plus the pre-release identifier for example "21-ea".    The build number 
and additional build information are useful in identifying the information 
about a JDK image but not available.  This proposes to add a new entry in the release file:

JAVA_RUNTIME_VERSION="$(VSTR)"

where `$(VSTR)` is the string represented by `Runtime::version()`.

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Commit messages:
 - JDK-8303476: Add the runtime version in the release file of a JDK image

Changes: https://git.openjdk.org/jdk/pull/12813/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12813&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303476
  Stats: 322 lines in 3 files changed: 173 ins; 149 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/12813.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12813/head:pull/12813

PR: https://git.openjdk.org/jdk/pull/12813