[lldb] Remove duplicated breakpoint tests

After reverting the deletion of the functionalities/breakpoint tests,
we now have some tests twice in the test/ folder which breaks dotest:

* commands/breakpoint/basic
* functionalities/breakpoint/breakpoint_command

After looking over these tests, I think it makes sense to only
keep the original functionalities/ folder. The commands/breakpoint/basic
test are not exclusively testing the breakpoint command itself, so
they shouldn't be in commands/ in the first place. Note that these
folders have identical contents (beside small adjustments regarding
the Makefile which landed after the restructuring).

llvm-svn: 371734