Add hook for pyttsx3.

[bwoodsend]

Add hook for pyttxs3. Fixes pyinstaller/pyinstaller#3268 and a rather long nabble thread.

We do have a hook and test already for pyttxs (without the 3) which is handled similarly but I'd prefer to keep them separate.

There's also a couple of extra commits tucked under here which I can't be bothered to separate into their own PRs. I'll merge this manually to keep the git history.

• 112f500 CI/CD: Oneshot: Allow custom bash install commands. This is so I can run any sudo apt install [dependencies] when needed.
• a7fedf0 CI/CD: Oneshot: Remove Python 3.5, add 3.9.

I've done oneshot testing in bits:

• scripts/cloud-test.py --os=windows --os=macos pyttsx3==2.90, pyttsx3==2.71
• scripts/cloud-test.py --os=windows --os=macos --py=all pyttsx3
• scripts/cloud-test.py --commands="sudo apt install espeak ffmpeg libespeak1" pyttsx3==2.90, pyttsx3==2.71
• scripts/cloud-test.py --commands="sudo apt install espeak ffmpeg libespeak1" --py=all pyttsx3

They all pass.