Applied clang-tidy modernize-use-override over LLDB and added it to the LLDB .clang-tidy config.
Differential Revision: https://reviews.llvm.org/D123340
The point is to allow users with a related set of script based commands
to organize their commands in a hierarchy in the command set, rather than
having to have only top-level commands.
Differential Revision: https://reviews.llvm.org/D110298