Refine debug launch configuration for Segger J-Link

[jreineckearm]

Review and refine the first version of the Segger J-Link support. In particular, the following should be checked:

• Can the default configuration snippets be safely reduced to use CLI arg defaults?
• Can some of the settings be safely filled in during debug launch, for example using commands from other CMSIS related extensions.
• The current default configuration uses the GUI variant of the Segger J-Link server. This should change to use its CL variant.

[jreineckearm]

Closed by #41