RFR: 8293873: Centralize the initialization of UL

[Johan Sjölen]

Hi,

May I please have a review of this change? It moves around some of the initialization code of UL to one place (namely `LogConfiguration::initialize`). It does not change how UL works after VM start up, and it should not change how UL works after VM shut down, but it might change how UL works before VM start up. I don't believe that this causes any breakage.

Tier 2 and 3 tests are currently running, all green so far.

Some more context is available at https://bugs.openjdk.org/browse/JDK-8293873

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Commit messages:
 - Simplify UL initialization

Changes: https://git.openjdk.org/jdk/pull/10307/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10307&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8293873
  Stats: 99 lines in 10 files changed: 12 ins; 40 del; 47 mod
  Patch: https://git.openjdk.org/jdk/pull/10307.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10307/head:pull/10307

PR: https://git.openjdk.org/jdk/pull/10307