RFR: 8255041: Zero: remove old JSR 292 support leftovers

[Roman Kennke]

On Tue, 20 Oct 2020 07:56:48 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> JDK-8000780 removed `ZeroInterpreter::method_handle_entry`, but left its helpers around. These have no uses, and can be eliminated. Attention @rkennke, who did the JDK-8000780 a while ago.
> 
> Testing:
>  - [x] Linux x86_64 fastdebug zero images
>  - [x] Linux x86_64 release zero bootcycle-images

Looks good to me, thanks!

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Marked as reviewed by rkennke (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/758