RFR: 8297640: Increase buffer size for buf (insert_features_names) in Abstract_VM_Version::insert_features_names

[Emanuel Peter]

As described in [JDK-8297640](https://bugs.openjdk.org/browse/JDK-8297640), the buffer is too small, I increased the size from 512 to 1024.

The string needs to be a few characters larger, now that we have the additional feature `avx512_ifma`, added in [JDK-8288047](https://bugs.openjdk.org/browse/JDK-8288047).

I manually tested it with `./java --version`, used to crash, now works.
Running larger test suite now...

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Commit messages:
 - 8297640: Increase buffer size for buf (insert_features_names) in Abstract_VM_Version::insert_features_names

Changes: https://git.openjdk.org/jdk/pull/11366/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11366&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8297640
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/11366.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11366/head:pull/11366

PR: https://git.openjdk.org/jdk/pull/11366