ESLint reads test manifests to make sure it knows what type of test file it is, so that it can apply the correct rules and environment.

Currently it is using multi-ini to read the files, however with the ongoing switch to .toml in bug 1821199, we should also update ESLint to read from .toml files as well.

It looks like there is a toml package on npm that we can probably use.

This switch would probably also fix bug 1781025.