[docs]: Update Core Concepts section to Stargate

[clevinson]

• Update "Core Concepts" docs #7948 "baseapp" updated similar to "basics" section update (with Amino codec references) @amaurymartiny
• Update "Core Concepts" docs #7948 transactions (document proto tx pathway, legacy amino accessible via REST, general info about proto wrapper, link to "interace" section where appropriate) @amaurymartiny
• Update "Core Concepts" docs #7948 update Node page @amaurymartiny
• update "Encoding" section @blushi
• docs: Add grpc & rest endpoints overview #8064 overview of legacy + gRPC gateway REST API, and Swagger UI (see comment)
• @amaurymartiny migrate old docs from interfaces/ to this section, & update them.
• update Events page to reflect TypedEvents (depends on x/ibc: implement ADR 032 typed events #7762)
• update Ocaps page to reflect ADR-033 (depends on ADR 033: Inter-Module Communication #7459)

Notes:

• remove mention of handler and only use the Msg service vocabulary.

[amaury1093]

The two remaining items on this list to be updated are:

• typed events
• OCAPS

Since the ADR/implementation PRs are still not ready yet, I propose to change the milestone to 0.42.

[clevinson]

Closing as we'll create specific doc issues when necessary.