RFR: 8286756: Cleanup foreign API benchmarks

[Jorn Vernee]

On Fri, 13 May 2022 15:48:29 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> This simple patch regularizes some of the foreign API benchmarks. Some of the changes are:
> 
> * use of capital names for var handle and layout constants
> * move shared layout and var handle constants in a new superclass, `JavaLayouts`
> * regularize aligned vs. unaligned benchmarks, especially in `LoopOverNonConstantHeap`. Since the API now aligns layouts by default, where the benchmark name doesn't say anything we assume aligned layout; for benchmarks that test specifically the use of unaligned layouts, we use the `_unaligned` prefix.

Marked as reviewed by jvernee (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/8705