Standardize specification links

[tomdaffurn]

We should standardize all the links to specs to a single host and version for each type.

The RFC links we are using point to several hosts:

• https://datatracker.ietf.org/
• https://www.rfc-editor.org/

OID4VCI has 2 versions

• https://openid.net/specs/openid-4-verifiable-credential-issuance-1_0.html
• https://openid.github.io/OpenID4VCI/openid-4-verifiable-credential-issuance-wg-draft.html

[frankhinek]

I tend to prefer the https://datatracker.ietf.org/ but no strong preference either way.

The OIDC specs hosted on GitHub are updated more regularly, so perhaps use those links until they stop updating so frequently? For example, the OID4VCI spec at the https://openid.net URL is from February 2024 whereas the other was updated yesterday (July 10 2024).