[clang-tools-extra] Enforce SL.con.3: Add check to replace operator[] with at() [Cont.] (PR #95220)

[Paul Heidekrüger via cfe-commits]

PBHDK wrote:

> Btw, I realize that this check is part of the [bounds profile](https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#SS-bounds) (Bounds.4), so for consistency it should probably be named `cppcoreguidelines-pro-bounds-...`. This becomes then the last remaining check to complete the bounds profile!

Does the fact that this check implements the bounds profile need to be mentioned anywhere else? Or is it enough to have it be implicit, e.g., via the name.

https://github.com/llvm/llvm-project/pull/95220