RFR: 8286117: Remove unnecessary indirection and unused code in UL [v2]

[Johan Sjölén]

> This PR cleans up some minor annoyances in the UL code.
> 
> Note that the change from `LogImpl` to `LogTagSet` is equivalent, we're essentially inlining the calls that `LogImpl` would have made. This simplifies understanding ("why do we need `LogImpl` here?" was my question, answer: We don't!)'
> 
> *Edit:* Passes tier1.

Johan Sjölén has updated the pull request incrementally with one additional commit since the last revision:

  Use _tagset

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8541/files
  - new: https://git.openjdk.java.net/jdk/pull/8541/files/ecd9b543..810c4436

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8541&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8541&range=00-01

  Stats: 7 lines in 1 file changed: 2 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8541.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8541/head:pull/8541

PR: https://git.openjdk.java.net/jdk/pull/8541