RFR: 8297444: Refactor the javacserver build tool [v4]

[Magnus Ihse Bursie]

> Now that the javacserver no longer has any ambitions outside being a buildtool customized for the JDK build process, a lot of abstractions and generalizations can be removed.
> 
> This will allow the actual behavior to be more clearly visible, and will help debugging the issues we are still seeing (most likely race conditions), and to convert the tool to use the ToolProvider API in the future.

Magnus Ihse Bursie has updated the pull request incrementally with one additional commit since the last revision:

  Use Server.class instead of hard-coding a string

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Changes:
  - all: https://git.openjdk.org/jdk/pull/11298/files
  - new: https://git.openjdk.org/jdk/pull/11298/files/82998663..414c8ac1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11298&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11298&range=02-03

  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/11298.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11298/head:pull/11298

PR: https://git.openjdk.org/jdk/pull/11298