Better LLDB frame information (bug#66604)

Better LLDB frame information (bug#66604)

Instead of modifying `frame-format` to be entirely machine-readable,
keep the original human-readable format and append a second,
machine-readable line that we remove after parsing.

* lisp/progmodes/gud.el
(gud-lldb-marker-filter): Parse the new line format and filter it out.
* lisp/progmodes/gud.el
(gud-lldb-def-python-completion-function): Rename to...
(gud--lldb-python-init-string): ...this and add modification
of `frame-format`, which seems easiest done from Python.
(gud-lldb-frame-format): Remove.
(gud-lldb-initialize): Update, remove no longer needed parts.