For #2691, stabilize deleteForward by reducing asyncness

[pbwolf]

This is a small addition to the backspace PR, doing the same for deleteForward.

What has changed?

• The deleteBackward PR is included in this PR
• deleteForward is registered with registerTextEditorCommand and does not await anything
• deleteForward skips reformatting
• 'async' and 'await' are removed from tests of deleteForward
• EditableDocument.delete, a disused subroutine of deleteForward, is removed

The reason to skipFormat is: formatting moves the selection past commas, which in combination with deleteForward makes commas resist deletion! This interplay is newly exposed by the non-async deleteForward. The (prior) async deleteForward async'ly moved the selection, which "undid" formatting's selection if the timing worked out right.

Fixes #2691 and #2611

My Calva PR Checklist

I have:

• Read How to Contribute.
• Directed this pull request at the dev branch. (Or have specific reasons to target some other branch.)
• Made sure I have changed the PR base branch, so that it is not published. (Sorry for the nagging.)
• Made sure there is an issue registered with a clear problem statement that this PR addresses, (created the issue if it was not present).
  • Updated the [Unreleased] entry in CHANGELOG.md, linking the issue(s) that the PR is addressing.
• Figured if anything about the fix warrants tests on Mac/Linux/Windows/Remote/Whatever, and either tested it there if so, or mentioned it in the PR.
• N/A Added to or updated docs in this branch, if appropriate
• Tests
  • Tested the particular change
  • Figured if the change might have some side effects and tested those as well.
• Formatted all JavaScript and TypeScript code that was changed. (use the prettier extension or run npm run prettier-format)
• Confirmed that there are no linter warnings or errors (use the eslint extension, run npm run eslint before creating your PR, or run npm run eslint-watch to eslint as you go).

Ping @PEZ, @bpringe, @corasaurus-hex, @Cyrik

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[PEZ]

Thanks so much for contributing this work, @pbwolf! And thanks for researching throughly and detailing the rationale for the changes. It all makes sense, I think. The only thing I wonder about is why we call it Now and non-async, instead of just sync, as is the pattern in JS land. But we can change that later.

It looks ready to merge, but the PRs are both marked Draft. Is there something you still want to change, @pbwolf?