4.21.2 - Updates for UC Mode and more

Updates for UC Mode and more

• Add "driver.uc_switch_to_frame(frame)"
  --> This resolves #2282
• Do some UC Mode refactoring
• Do some refactoring
• Add driver methods
• Add option for setting "--host-resolver-rules=RULES"
  --> This resolves #2281
• Refresh Python dependencies

What's Changed

• Updates for UC Mode and more by @mdmintz in #2283

Full Changelog: v4.21.1...v4.21.2