Pass through documents and tutorials to remove uses of Indy SDK and general cleanup

[swcurran]

As we ramp down the use of the Indy SDK, we need to make sure that none of the documentation and tutorials guide a user to use anything other than Askar. A recent report (#2311) reported start up problems when following the guide, including having the user using —wallet-type indy. We need to remove such references.

In doing that, other clean up items might include:

• Making sure that the messages prefix is no longer ever using the did:sov:… style, but instead is using the https://didcomm.org prefix.
• Checking that all the tutorials still work.
• <TBD — I’m sure there are other things…>
• Fixing typos.

[swcurran]

@esune — this is a good one for a new ACA-Py contributor. Perhaps Gurjeet could plan on doing this as he ramps up.