RFR: 8272735: Add missing SubL node transformations

[Ahmed Muhsin]

This change adds/enables missing subnode transformations for operations of type `long`.
A few comments in the test file `SubINodeIdealizationTests.java` were modified to add clarity and to fix a typo.
Hotspot:tier1 tests were run, this change does not introduce any new failures.

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Commit messages:
 - modify test method comments to add clarity and validity
 - reorder test methods to match the test's counterpart, SubINodeIdealizationTests.java
 - add missing SubLNode transformations
 - add tests for missing SubLNode transformations

Changes: https://git.openjdk.java.net/jdk/pull/7669/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7669&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8272735
  Stats: 64 lines in 3 files changed: 29 ins; 0 del; 35 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7669.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7669/head:pull/7669

PR: https://git.openjdk.java.net/jdk/pull/7669