Update for streamlink release 4.0+

[TheKeeperOfPie]

Fixes:

• Windows build instruction to include missing dependencies
• Enforced minimum Python 3.9 by removing old workflows
• Updates JSON parsing to account for new windows-installer config

Test: manual, bring up a fresh Ubuntu WSL2 instance and invoke builds for win32 and amd64

[Neustradamus]

@TheKeeperOfPie, @beardypig: Any progress on this PR?