RFR: 8339592: Simplify and remove unused code in ObjectMethods.<clinit>

[Chen Liang]

On Thu, 5 Sep 2024 08:19:44 GMT, Claes Redestad <redestad at openjdk.org> wrote:

> A few trivial(?) cleanups to `java.lang.runtime.ObjectMethods`:
> - Avoid `MethodType.fromMethodDescriptorString` which needs a classloader
> - Use `MethodHandles.zero`
> - Remove unused static `MethodHandles` and `MethodTypes`

Marked as reviewed by liach (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/20866#pullrequestreview-2283086658