This commit cleans up the includes in the `lldb-dap` subfolder. The main
motivation was that I got annoyed by `clangd` always complaining about
unused includes while working on lldb-dap.
This adds a layer between `SounceBreakpoint`/`FunctionBreakpoint` and
`BreakpointBase` to have better separation and encapsulation so we are
not directly operating on `SBBreakpoint`.
I basically moved the `SBBreakpoint` and the methods that requires it
from `BreakpointBase` to `Breakpoint`. This allows adding support for
data watchpoint easier by sharing the logic inside `BreakpointBase`.
