optimize github actions jobs to avoid redundant runs

[morsecodist]

Our workflows are SUPER long now so I added some stuff to prevent them from running in certain contexts:

• New workflows cancel previously running workflows to keep stuff from getting clogged
• CI only runs on the directories you have made changes in
• If linting fails the other CI jobs are cancelled
• Only run the mngs benchmark if there is mngs diff

I experimented with the different diffs to show it is working. I added and removed some mngs diff which is why the benchmarks ran on the last commit.

[tfrcarvalho]

Nit: can you make the title of the PR more specific? You scared me a bit there...

Cancelation is per branch, right?

[morsecodist]

@tfrcarvalho sorry done, and yes I confirmed it is per branch

[tfrcarvalho]

Looks great, thanks!