AIP-2 base64url consistency

[shaangill025]

• In regards to decoding, we handle base64 permissively, passing urlsafe as True.
• If emit_new_didcomm_mime_type and emit_new_didcomm_prefix arguments are set, send everything as base64url [updates data_base64 accordingly] else leave eveything as it is.
  closes raw base64url consistency? #1108

[swcurran]

The concern I have is the use of the emit_new_didcomm_mime_type and emit_new_didcomm_prefix arguments as the trigger. Should we have a separate aip2 argument as a trigger for a number of behaviours in ACA-Py? Alternative is a new one specifically for this, but aren't we trying to make a number of breaking changes at once?

[shaangill025]

Can use --aip-version argument as the trigger, once the following PR is merged.
#1056

[shaangill025]

This PR should be ready, it needs minor change [uncommenting # if self._session.profile.settings.get_value("aip_version", 1) >= 2] once #1056 is merged into main.

[dbluhm]

@shaangill025 Is this PR still relevant?