RFR: CODETOOLS-7903307: Move ASM dependent classes to a different package

[Alexandre Iline]

This change is moving all classes which directly depend on ASM into a sub-package. This is done in a separate step to allow a diff which would be possible to review line by line, to make sure there are no changes in behavior.
To accommodate the move:
1. Bunch of imports, obviously
2. Bunch of methods increased visibility to public, or, in rare cases, to protected
3. A few field usages are replaced with getters.
Further refactoring is due, see the bug for more information.

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Commit messages:
 - CODETOOLS-7903307: Move ASM dependent classes to a different package

Changes: https://git.openjdk.org/jcov/pull/24/files
 Webrev: https://webrevs.openjdk.org/?repo=jcov&pr=24&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903307
  Stats: 372 lines in 59 files changed: 156 ins; 82 del; 134 mod
  Patch: https://git.openjdk.org/jcov/pull/24.diff
  Fetch: git fetch https://git.openjdk.org/jcov pull/24/head:pull/24

PR: https://git.openjdk.org/jcov/pull/24