[GH] Move presubmit to pull request instead of pull request target
[GH] Move presubmit to pull request instead of pull request target

This PR updates the presubmit workflow to run on pull request.
It does not need the secrets anoymore since they are moved to
workflow_run actions.

We probably also don't need the repo checkout calculations anymore
but i wanted to minimize changes.

Bug: n/a
Test: n/a

This is an imported pull request from https://github.com/androidx/androidx/pull/202.

Resolves #202
Github-Pr-Head-Sha: 5d3efca98f6bcfb2fd2d60362388c443f46919ba
GitOrigin-RevId: d7f76a1a72a4f978b2d1a0a7ac782b06eecc9bf0
Change-Id: I1bfd60e11a229dbc3b061e78ce12f487a3f89613

AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx