[clang-tools-extra] [clang-tidy] Add a release note about unchecked-optional-access smart pointer caching (PR #122290)

[Jan Voung via cfe-commits]

jvoung wrote:

> does check doc need to be changed also?

Good question -- I don't see the option IgnoreSmartPointerDereference advertised in the check docs.

Otherwise, we partially updated the check docs about earlier accessor caching. Updated more to mention smart pointer like APIs. Also previously updated internal code comments about IgnoreSmartPointerDereference in the `UncheckedOptionalAccessModelOptions` struct.

https://github.com/llvm/llvm-project/pull/122290