fix ConvertToMessageFormatFixCore and ConvertToStringFormatFixCore to refine the logic for determining when to use a text block vs a single line - logic now only uses text block if there are 3 or more lines used in the concatenation AND the number of string literal characters is greater than 80
modify existing tests and add new tests to AssistQuickFixTest15
What it does
See commit message.
How to test
See issue or new tests.
Author checklist