Support `.ava` cacheDir for better compatibility with Yarn PnP

Hello,

We're using Yarn 3 with PnP in our mono-repo, and find that ava is creating unwanted node_modules directories in our workspace (with node_modules/.cache/ava/failing-tests.json) This is a result of https://github.com/avajs/ava/blob/f047694d86a8ee7af2e998baf28812770e9ea71e/lib/cli.js#L256

Sometimes the existence of node_modules confuses the pnp patched executables (eg. eslint), so the mere existence of node_modules can sometimes cause issues with things working reliable.

It would be great if you supported some manner of specifying the cache directory or simply defaulted to projectDir/.ava and recommended adding .ava to the .gitignore.

Thanks!