Refactor command bot and drop rejecting non paritytech members

[mordamax]

Aims to

• close cmd-bot for the people! #7049
• close https://github.com/paritytech/opstooling/issues/449
• close https://github.com/paritytech/opstooling/issues/463
• close /cmd bench with all runtimes fails #6940

What's changed:

• removed is paritytech member check as required prerequisite to run a command
• run the cmd.py script taking it from master, if someone who run this is not a member of paritytech, and from current branch, if is a member. That keeps the developer experience & easy testing if paritytech members are contributing to cmd.py
• isolate the cmd job from being able to access GH App token or PR token- currently the fmt/bench/prdoc are being run with limited permissions scope, just to generate output, which then is uploaded to artifacts, and then the other job which doesn't run any files from repo, does a commit/push more securely

[paritytech-workflow-stopper]

All GitHub workflows were cancelled due to failure one of the required jobs.
Failed workflow url: https://github.com/paritytech/polkadot-sdk/actions/runs/12906645216
Failed job name: test-linux-stable

[bkchr]

Nice work @mordamax :)