chore: clarify that Wallet Instance types do not change federation processing

[peppelinux]

This PR resolves #64

It:

• states that Wallet Instance types are informative and that federation processing does not vary by type.
• keeps the Mobile / Web / PWAW descriptions as deployment context.
• makes explicit that trust with the Holder uses the Wallet Provider and Wallet Attestation for every instance type.

[samuelmr]

Still not sure why this specification needs to define wallet instance types if the behaviour of all types of wallet instances is equal.

[peppelinux]

@samuelmr there reason why we should not remove the Wallet Instance types is because they are not federation Entity Types and they do not change processing.

Issuers, Verifiers, and other Entities always establish trust with the Holder through the Wallet Provider and the Wallet Attestation. That is the same for a native mobile app, a custodial or non-custodial web/cloud wallet, and a PWA.

They are in the document as informative deployment forms, as requested by community roughly 1.5 years ago, for two reasons:

• This profile is not limited to native mobile wallets. Wallet Solutions are already described as mobile apps, cloud services, or other software, instantiated on a Personal Device or a Remote Service. So implementers do not assume a mobile-only architecture.

• The Holder stays outside the Trust Chain. Some deployments, especially organizational or custodial cloud wallets, look as if the instance itself could be a Federation Entity (while it is not). The list exists so the spec can state, in one place, that this is not the case. The Holder won't stay the Trust Chain according to this architecture, regardless of how the Wallet Instance is implemented (and we list all the implementation type to definitively clarify this).

[fmarino-ipzs]

LGTM, thanks. I only left a couple of editorial suggestions.