- Move sys_info into an internal module to avoid having so many
top level modules for Blender's internal functionality.
- Rename system_info sub-modules that pre-fill URL's for clarity.
- Move top-level exception handling into the operator.
- Report an error if an unexpected exception occurs.
- Use `Exception` instead of `BaseException` as there is no reason to
catch the additional exceptions.
- Remove use of sys_info from the command line example,
replace with in-lined system info.
Add support for add-ons to define commands using the new argument
`-c` or `--command`.
Commands behave as follows:
- Passing in a command enables background mode without the need to pass
in `--background`.
- All arguments following the command are passed to the command
(without the need to use the `--` argument).
- Add-ons can define their own commands via
`bpy.utils.register_cli_command` (see examples in API docs).
- Passing in `--command help` lists all available commands.
Ref !119115
