8338867: GenShen: Do all size accounting in words

[kdnilsen]

Draft while I work through the details of this

We want to consistently do all size accounting in words rather than a mix of bytes and words. This will affect both traditional Shenandoah and Generational Shenandoah implementations.

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Progress

• [x] Change must not contain extraneous whitespace
• [x] Commit message must refer to an issue
• [ ] Change must be properly reviewed (1 review required, with at least 1 Committer)

Issue

• JDK-8338867: GenShen: Do all size accounting in words (Enhancement - P4)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/shenandoah.git pull/482/head:pull/482
$ git checkout pull/482

Update a local copy of the PR:
$ git checkout pull/482
$ git pull https://git.openjdk.org/shenandoah.git pull/482/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 482

View PR using the GUI difftool:
$ git pr show -t 482

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/shenandoah/pull/482.diff