Updates no-relative-monorepo-import regex to handle more scenarios:
❌ Scenarios that will violate the rule:
```ts
import { something } from '../../payload/src/utilities/some-util.js'
import { something } from '../../../packages/payload/src/utilities/some-util.js'
import { something } from 'packages/payload/src/utilities/some-util.js'
```
- Upgrades eslint from v8 to v9
- Upgrades all other eslint packages. We will have to do a new
full-project lint, as new rules have been added
- Upgrades husky from v8 to v9
- Upgrades lint-staged from v14 to v15
- Moves the old .eslintrc.cjs file format to the new eslint.config.js
flat file format.
Previously, we were very specific regarding which rules are applied to
which files. Now that `extends` is no longer a thing, I have to use
deepMerge & imports instead.
This is rather uncommon and is not a documented pattern - e.g.
typescript-eslint docs want us to add the default typescript-eslint
rules to the top-level & then disable it in files using the
disable-typechecked config.
However, I hate this opt-out approach. The way I did it here adds a lot
of clarity as to which rules are applied to which files, and is pretty
easy to read. Much less black magic
## .eslintignore
These files are no longer supported (see
https://eslint.org/docs/latest/use/configure/migration-guide#ignoring-files).
I moved the entries to the ignores property in the eslint config. => one
less file in each package folder!
