Set up different environments for GCP build triggers

[jiggoha]

Make sure we have:

• trigger for presubmit (based on the short-lived PR branches) that will test that a manifest can be generated etc, but won't put this in a long-lived log
• trigger for merge-to-main (based on the main branch) that will build every commit, build the manifest, and put it in the CI log
• trigger for release tag (based on the main branch) that will sign a release manifest for the binary and put it in the prod log

The delta is that we to add the trigger for a presubmit.

[jiggoha]

Update:

• Merged Add presubmit Cloud Build trigger. armored-witness-applet#177 for the applet
• Created presubmit config for recovery tool in Add documentation and Cloud Build configs for releasing the recovery tool. armored-witness-boot#53
• Created presubmit config for boot in Add documentation and Cloud Build configs for releasing the bootloader. armored-witness-boot#56
• Created presubmit config for OS in Add presubmit Cloud Build config. armored-witness-os#129