RFR: 8261750: Remove internal class sun.net.www.MimeLauncher

[Julia Boes]

This change removes sun.net.www.MimeLauncher, a package-private class that is no longer used.

The sun.net.www package is exported to java.net.http and jdk.jartool. The only public access point to a MimeLauncher instance is sun.net.www.MimeEntry::launch, which is not called anywhere in those two package. A related public class, sun.net.www. ApplicationLaunchException, is no longer used anywhere. Therefore, these two can also be considered for removal.

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Commit messages:
 - remove MimeLauncher and related

Changes: https://git.openjdk.java.net/jdk/pull/2580/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2580&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8261750
  Stats: 301 lines in 3 files changed: 0 ins; 300 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2580.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2580/head:pull/2580

PR: https://git.openjdk.java.net/jdk/pull/2580