[jdk17u] RFR: 8269280: (bf) Replace StringBuffer in *Buffer.toString()

[Aleksey Shipilev]

On Mon, 23 Aug 2021 09:08:09 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Clean backport to improve performance in post-BiasedLocking world.
> 
> Additional testing: 
>  - [x] `java/nio/Buffer` tests are passing
>  - [x] Re-generating the test code from the new template yields the same contents

Got the push approval for 17.0.2.

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PR: https://git.openjdk.java.net/jdk17u/pull/35