RFR: 8303418: Improve parameter and variable names in BitMap [v2]

[Kim Barrett]

On Thu, 2 Mar 2023 07:42:16 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

> Not 100% sold on the use of `bit` for a single bit index. But at least consistency makes it clearer.

In this change I was mostly trying to remove outliers in parameter naming.
I'm not wedded to either `bit` or `word`, but that is the common usage.

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PR: https://git.openjdk.org/jdk/pull/12798