[lldb] Add scripted process launch/attach option to {,platform }process commands

This patch does several things:

First, it refactors the `CommandObject{,Platform}ProcessObject` command
option class into a separate `CommandOptionsProcessAttach` option group.

This will make sure both the `platform process attach` and `process attach`
command options will always stay in sync without having with duplicate
them each time. But more importantly, making this class an `OptionGroup`
allows us to combine with a `OptionGroupPythonClassWithDict` to add
support for the scripted process managing class name and user-provided
dictionary options.

This patch also improves feature parity between `ProcessLaunchInfo` and
`ProcessAttachInfo` with regard to ScriptedProcesses, by exposing the
various getters and setters necessary to use them through the SBAPI.

This is foundation work for adding support to "attach" to a process from
the scripted platform.

Differential Revision: https://reviews.llvm.org/D139945



Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>