AVA 6 watch mode

[novemberborn]

Rely on recursive fs.watch(), rather than Chokidar. On Linux this is supported from Node.js 20 onwards. It won't work for network shares and Docker volume mounts which would require polling, we'll find out if that's a problem or not.

Use @vercel/nft to perform static dependency analysis, supporting ESM and CJS imports for JavaScript & TypeScript source files. This is a huge improvement over the previous runtime tracking of CJS imports, which did not support ESM.

Rewrite the change handling logic to be easier to follow (though it's still pretty complicated).

Improve integration with @ava/typescript. The watcher can now detect a change to a TypeScript source file, then wait for the corresponding build output to change before re-running tests. See avajs/typescript#46.

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Because this is a big change, and due to the Linux and network share implications, the previous implementation can be enabled:

export default {
	watcher: 'ava5+chokidar'
}

You will need to manually install chokidar however.

Tests for the previous implementation have been removed. They've been hard to maintain. We're not expecting to make any / many code changes so hopefully we'll be all right.

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Other changes:

• Remove undocumented ability to start watch mode via the config. Require the CLI flag instead.
• Add ava.config.mjs to default watcher ignore patterns
• Ignore changes to failed-tests file in watcher