RFR: 8294402: Add diagnostic logging to VMProps.checkDockerSupport

[Mikhailo Seledtsov]

Add log() and logToFile() methods to VMProps for diagnostic purposes.

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Commit messages:
 - Minor fixes in printed message
 - Log to stderr as per discussion
 - Fixed issues with process out/err redirect
 - Simplification and refactoring
 - Draft: redirect container ps child output to log file
 - More logging for container methods
 - Allow both absolute and relative path for log file
 - Add diagnostic logging to at-requires VMProps

Changes: https://git.openjdk.org/jdk/pull/12239/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12239&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8294402
  Stats: 40 lines in 1 file changed: 38 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/12239.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12239/head:pull/12239

PR: https://git.openjdk.org/jdk/pull/12239