RFR: 8368817: Convert JDK_Version::to_string to use stringStream instead of jio_snprintf-chain

[Kim Barrett]

Please review this change to JDK_Version::to_string to use stringStream to
accumulate the version string in the buffer, rather than using jio_snprintf to
write the various pieces.

Testing: mach5 tier1
Locally manually examined result of JDK_Version for builds configured with
different values for various version parameters.

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Commit messages:
 - JDK_Version::to_string

Changes: https://git.openjdk.org/jdk/pull/27567/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27567&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8368817
  Stats: 17 lines in 1 file changed: 0 ins; 10 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/27567.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27567/head:pull/27567

PR: https://git.openjdk.org/jdk/pull/27567