change(web): adjust TokenizationCorrector spec 🚂 🔪

[jahorton]

This PR makes a number of smaller adjustment to the TokenizationCorrector type to prepare it further for direct use in actual correction-searching processes:

1. When part of the corrector's range is unable to yield a viable correction, the TokenizationCorrector will behave as follows:
   • If NO part can yield a viable correction, it will not return any correction result, signaling 'none'.
   • If there at least one correction has been found that was viable, results will be produced, but with no actual correction et for the uncorrectable part.
2. The corrector now tracks how many codepoints are currently considered 'correctable' - useful for comparison against the total number of detected correction-edits.
   • A current standing engine principle - if there are edits, and the number of edits matches the full codepoint length, that's a 100% replacement, with none of the original text remaining - a case very inefficient to consider that should thus be ignored.

Build-bot: skip build:web
Test-bot: skip

[keymanapp-test-bot]

User Test Results

Test specification and instructions

User tests are not required

Test Artifacts

• Web
  • KeymanWeb Test Home - build : all tests passed (no artifacts on BuildLevel "build")