RFR: 8368024: Remove StringConcatFactory#generateMHInlineCopy

[Claes Redestad]

On Thu, 18 Sep 2025 21:11:54 GMT, Shaojin Wen <swen at openjdk.org> wrote:

> With the introduction of [8336856: Efficient hidden class-based string concatenation strategy](https://github.com/openjdk/jdk/pull/20273) , the StringConcatFactory#generateMHInlineCopy method is no longer used by default.
> 
> After a year of community use, the InlineHiddenClassStrategy has proven to work well, so I recommend removing the implementation of StringConcatFactory#generateMHInlineCopy.

LGTM

Thanks for the drive-by fix to that erroneous indexCoder javadoc param

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Marked as reviewed by redestad (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/27374#pullrequestreview-3251142201