Update diagrams with latest terminology used (Trust Authority, SP-IdP-Proxy)

[dianagudu]

Update diagrams in the informational document on Establishing trust between OAuth2 proxies [AARC-I058] to include the current terminology used:

• Trust Anchor -> Trust Authority
• Infra Proxy -> SP-IdP-Proxy

Additionally, add a note in Terminology section that refers to AARC-G045 as a source for a number of terms used in the document, e.g. Infra Proxy.

[dianagudu]

Links to all diagrams, for reference:

• 2 Generic flow for establishing trust between two proxies
• 2.1 Establishing trust with shared list of trusted entity identifiers
• 2.2 Establishing trust with shared aggregated entity statements
• 2.3 Establishing trust with targeted entity statement resolution: Resolve by subject ID
• 2.4 Establishing trust with shared list of trusted entity identifiers with OpenID Federation Metadata
• 2.5 Federation entity discovery
• 2.5 Proxy A evaluates trust of proxy B
• 2.5 Proxy B evaluates trust of proxy A