[jdk17u-dev] RFR: 8283199: Linux os::cpu_microcode_revision() stalls cold startup

Mon Oct 24 09:32:29 UTC 2022

Unclean backport to fix the startup time regression.

The backport is not clean, because [JDK-8238161](https://bugs.openjdk.org/browse/JDK-8238161) is not present in JDK 17, and thus we have `fopen` instead of `os::fopen` in these hunks.

Verified the startup time improves, using the scripts from the issue.

# Before
real	0m0.042s
real	0m0.043s
real	0m0.043s

# After
real	0m0.025s
real	0m0.024s
real	0m0.024s

Additional testing:
 - [x] Linux x86_64 fastdebug `tier1`

-------------

Commit messages:
 - Backport 1443f6b9191c127abdae38cadb1a44af3c652f1d

Changes: https://git.openjdk.org/jdk17u-dev/pull/820/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=820&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8283199
  Stats: 19 lines in 1 file changed: 16 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/820.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev pull/820/head:pull/820

PR: https://git.openjdk.org/jdk17u-dev/pull/820