RHCLOUD-33054 - Pipeline to sync protos

[lennysgarage]

@merlante suggestion about moving where the pipeline for syncing proto files simplifies things quite a bit.

Addressing comments from project-kessel/relations-api#143 (review):

1. Using the peter-evans/create-pull-request action helps simplify a lot of the pull request business. "The default behaviour of the action is to create a pull request that will be continually updated with new changes until it is merged or closed" - https://github.com/peter-evans/create-pull-request?tab=readme-ov-file#action-behaviour
2. Pipeline here runs a cronjob every 6 hours that pulls the relations-api copies any changes over and creates a PR, no PR is opened if no changes are made.
3. Similar action could be added to go & python clients. Should be relatively simple to copy, just requires updating paths.
4. Shouldn't be a problem since the protos will have been already committed to the main branch in the source of truth repo relations-api

Currently scheduled to run every 6 hours, but can also be manually triggered so if you want to copy right away you can.
Example PR: lennysgarage#6

Can also mostly resolve: #14

JIRA: https://issues.redhat.com/browse/RHCLOUD-33054

[merlante]

LGTM