Refactor Manual-Advance to `Dialogic.Inputs.manual_advance`

[CakeVR]

Evens out the difference between Auto-Advance, Auto-Skip, and Manual-Advance by turning it into a property on the Inputs-subsystem.

This has a breaking impact on the API and results in the following changes:

Setting the enable state of Manual-Advance:

# Old:
Dialogic.Inputs.set_manualadvance(true, false)

# New:
Dialogic.Inputs.manual_advance.enabled_forced = true
Dialogic.Inputs.manual_advance.enabled_until_next_event = false

Getting the enable state of Manual-Advance:

# Old:
var result := Dialogic.Inputs.is_manualadvance_enabled()

# New:
var result := Dialogic.Inputs.manual_advance.is_enabled()

[Jowan-Spooner]

Thank you, it's great having them all match!