RFR: 8245455: Remove alternative StringConcatFactory strategies

[Jim Laskey]

LGTM.


> On May 22, 2020, at 6:52 AM, Claes Redestad <claes.redestad at oracle.com> wrote:
> 
> Hi,
> 
> this patch removes the alternative, undocumented strategies from
> StringConcatFactory.
> 
> The default strategy has been optimized and stabilized since inception in JDK 9, while the alternative strategies have been falling behind
> both in terms of performance and stability - while adding maintenance
> cost.
> 
> The removal allows some simplifications to the code that will reduce
> per callsite bootstrap overhead, and reduce what we need to load eagerly
> during bootstrap. I've also applied the pattern from JDK-8218173 to
> the remaining Stringifier method handles, which further improve
> robustness of bootstrapping under an OOME condition.
> 
> Webrev: http://cr.openjdk.java.net/~redestad/8245455/open.00/
> Bug:    https://bugs.openjdk.java.net/browse/JDK-8245455
> 
> Testing: tier1-3
> 
> Thanks!
> 
> /Claes