add 64 split_bs and tsangan Community Layouts

[dunk2k]

Description

1. add split_bs variant of 64_ansi and 64_iso Community Layouts
2. Can be argued that 64_* Community Layouts are a further variation of 60% Arrow layouts; with adding _tsangan layouts to 60% Arrow layouts in add 60 arrow tsangan Community Layouts #22572, this PR does the same as mentioned PR but for 64 Community Layouts.

Mutli-layout 60% boards with both 2u/1u-1u Left Shift on shift/4th row and Tsangan bottom row are accommodating of 64_*_tsangan* layouts.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Issues Fixed or Closed by This PR

• n/a

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[dunk2k]

reopen when both #22556 and #22572 are merged