[lldb/Lua] add support for Lua function breakpoint

Adds support for running a Lua function when a breakpoint is hit.

Example:
   breakpoint command add -s lua -F abc

The above runs the Lua function 'abc' passing 2 arguments. 'frame', 'bp_loc' and 'extra_args'.

A third parameter 'extra_args' is only present when there is structured data
declared in the command line.

Example:
   breakpoint command add -s lua -F abc -k foo -v bar

Differential Revision: https://reviews.llvm.org/D93649