Update CI to use pull_request_target

[tomek0123456789]

Which component is your feature related to?

Forge, Cast

Feature Request

Right now, when an external contributor wants to open a PR from a fork and we approve the CI run, the secrets we're using in tests aren't available to that run (GitHub security reasons).

• Update CI to fix secret fetching
  • Look into Preventing pwn requests blogpost
• Additionally, update documentation with information that external contributors need to set secrets in their fork repository

[tomek0123456789]

Closing since we are reverting the changes.