RFR: 8294186: AArch64: VectorMaskToLong failed on SVE2 machine with -XX:UseSVE=1

[Eric Liu]

C2_MacroAssembler::sve_vmask_tolong would fail on BITPERM supported SVE2 machine with "-XX:UseSVE=1".

`BITPERM` is an optional feature in SVE2. With this feature, VectorMaskToLong has a more efficent implementation. For other cases, it should generate SVE1 code.

[TEST]
jdk/incubator/vector, hotspot/compiler/vectorapi passed on BITPERM supported SVE2 machine, with option -XX:UseSVE=(0, 1, 2).

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Commit messages:
 - 8294186: AArch64: VectorMaskToLong failed on SVE2 machine with -XX:UseSVE=1

Changes: https://git.openjdk.org/jdk/pull/10443/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10443&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8294186
  Stats: 28 lines in 1 file changed: 13 ins; 13 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/10443.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10443/head:pull/10443

PR: https://git.openjdk.org/jdk/pull/10443