[Tech] Dependabot doesn't update the lock file + replace npm with pnpm

[glushkova91]

Let's try to fix/adjust Dependabot to start actively using it.

1. Dependabot should maintain the lock file together with dependencies versions updates. Currently it's not happening, hence all auto PR's build failing. That might be because in dependabot.yml we specified directory: "/core/" and pnpm-lock.file is in root directory, maybe we need to change it to root.
2. Dependabot start supporting pnpm in 2023 and in our config package-ecosystem is still npm. Let's update it.