Add `ignore start` and `ignore stop` coverage ignore hints

[AriPerkkio]

Clear and concise description of the problem

In Vitest v3 it was possible to use ignore start and ignore stop code coverage ignore hints on V8 coverage. This was possible due to usage of v8-to-istanbul. However v8-to-istanbul had really limited support for ignore hints as it doesn't operate on AST level - it did not support ignore if, ignore else or ignore next. Also v8-to-istanbul reports inaccurate coverage results which was the main reason to replace it.

Users on Vitest v3 got used to ignore start and ignore stop and have been asking its support in:

• Vitest 4 - Vue template ignores #8801
• How to disable coverage report for <template> and <style> section in the vue file #3183

One major difference in v8-to-istanbul's ignore hint support is that it "parsed" (regex match against text file) the original source file instead of the transpiled runtime code. This made it possible to use ignore hints even when the compiler (99% of times Vue) removed comments, or placed the generated code on different line.

Note that istanbul-lib-instrument has never supported ignore start/stop in its 13 years of existence. This is just a work-around v8-to-istanbul had to come up with due to its lack of AST analysis.

Suggested solution

Add support for ignore start and ignore stop to upstream packages. These ignore hints should be parsed from the original source text file, not from the transpiled runtime code.

Alternative

Have the same conversation over and over again explaining the difference between these coverage tools.

Additional context

Support for V8 coverage:

• feat: support ignore start and ignore stop AriPerkkio/ast-v8-to-istanbul#109

Support for Istanbul coverage:

• feat: support ignore start and ignore stop istanbuljs/istanbuljs#835

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