RFR: 8339870: Remove yet more stale TODOs [v3]

[William Kemper]

> Final round of TODO removal.
> * Move asterisk for pointer next to type, not variable
> * Remembered set verifier uses a small 'scanner' abstraction to simplify reading of read or write card table
> 
> ## Testing
> 
> GHA, Internal pipelines

William Kemper has updated the pull request incrementally with three additional commits since the last revision:

 - Fix typo in comment
 - parseable -> parsable (again)
 - Improve comments

-------------

Changes:
  - all: https://git.openjdk.org/shenandoah/pull/496/files
  - new: https://git.openjdk.org/shenandoah/pull/496/files/135cc5ec..db8a0e95

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=shenandoah&pr=496&range=02
 - incr: https://webrevs.openjdk.org/?repo=shenandoah&pr=496&range=01-02

  Stats: 40 lines in 8 files changed: 4 ins; 17 del; 19 mod
  Patch: https://git.openjdk.org/shenandoah/pull/496.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/496/head:pull/496

PR: https://git.openjdk.org/shenandoah/pull/496