RFR: JDK-8311249: Remove unused MemAllocator::obj_memory_range

[Aleksey Shipilev]

On Mon, 3 Jul 2023 17:46:13 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> This is a leftover from [JDK-8171221](https://bugs.openjdk.org/browse/JDK-8171221), which removed its only use.
> Gets into the way of [JDK-8139457](https://bugs.openjdk.org/browse/JDK-8139457).
> 
> Additional testing:
>  - [x] GHA builds

Thank you!

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PR Comment: https://git.openjdk.org/jdk/pull/14759#issuecomment-1619836289