RFR: 8366272: The os::xxx APIs do not manage errno correctly

[Anton Artemov]

Hi, please consider the following changes:

In this PR the handling of `errno` is improved by inspection of the codebase and fixing potential overwrites of `errno` by other methods. Potential overwrites are addressed using `ErrnoPreserver` functionality where necessary. 

Tested in tiers 1 - 5.

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Commit messages:
 - 8366272: Improved errno management in os:xxx methods

Changes: https://git.openjdk.org/jdk/pull/28086/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28086&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8366272
  Stats: 18 lines in 6 files changed: 16 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/28086.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28086/head:pull/28086

PR: https://git.openjdk.org/jdk/pull/28086