RFR: 8297041: Remove the last remnants of sjavac

[Magnus Ihse Bursie]

The sjavac ("smart javac") was an ambitious project. It should parallelize java compilation, create a background daemon process that kept the JVM "hot" with the JITted javac code, define a public api so only noticeable changes in a class caused further dependency compilations, etc etc.

Some of this never came to fruition. Other were implemented differently, as the `depend` plugin. The only thing we're currently using (and have been for the last few years) is the "server" functionality, that is, the ability to keep a single JVM process alive, and reuse the JITted code.

This code does not belong in the jdk.compiler module. It is a buildtool, pure and simple. Let's move it to it's proper place.

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Commit messages:
 - Update copyright year for javac server files
 - One more sjavac reference in test
 - Remove last references to sjavac
 - Move compilation of javac server to interim langtools
 - Update package in compilation as well
 - Remove or rename remaining references to sjavac
 - Change package name to javacserver
 - Clean up Options
 - Move javac server to buildtools
 - Cut last ties to javac internals...
 - ... and 4 more: https://git.openjdk.org/jdk/compare/d0fae43e...2124c86b

Changes: https://git.openjdk.org/jdk/pull/11185/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11185&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8297041
  Stats: 12695 lines in 118 files changed: 1058 ins; 11574 del; 63 mod
  Patch: https://git.openjdk.org/jdk/pull/11185.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11185/head:pull/11185

PR: https://git.openjdk.org/jdk/pull/11185