Avoid doing MH creation when initializing `StringConcatFactory` by lazily initializing to a `@Stable` field instead.
------------- Commit messages: - 8288425: Footprint regression due MH creation when initializing StringConcatFactory Changes: https://git.openjdk.org/jdk/pull/9154/files Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=9154&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8288425 Stats: 11 lines in 1 file changed: 7 ins; 0 del; 4 mod Patch: https://git.openjdk.org/jdk/pull/9154.diff Fetch: git fetch https://git.openjdk.org/jdk pull/9154/head:pull/9154 PR: https://git.openjdk.org/jdk/pull/9154
