Remove AccountInfo usage in Context / derive(Accounts) macro and migrate to UncheckedAccount

[nutafrost]

We need to remove AccountInfo types from contexts in the derive(Accounts) macro and related places, replacing them with UncheckedAccount (or other appropriate wrappers) and making sure consumer code, tests, and documentation are updated accordingly.

Impact

Users who currently define accounts in contexts using AccountInfo will need to update their code.
Example programs and tests in Anchor will reflect the new usage pattern (UncheckedAccount).
There might be build/test failures in user code if not migrated.
Documentation and macro behavior around derive(Accounts) will shift, so users need to adapt.

[nutafrost]

#2470