With the new ESM version of `ng-dev`, the TypeScript config loading
cannot happen automatically because `ts-node` cannot hook into the
Node ESM module resolution at runtime. To fix this `ng-dev` is now
loading a plain `.ng-dev/config.mjs` and the runtime just needs to be
configured accordingly, i.e. running `ng-dev` with `ts-node` so that
the ESM loader can be wired up before Node's runtime starts (using e.g.
`node --loader`).
PR Close#46437
Checks the `.ng-dev` tool configuration in CI, compared
to doing it locally when the caretaker intends to perform
a merge and then realizes the config is broken.
PR Close#43322
