Resolve warning for missing MCU debugger

This is a follow-up to the comment by omrahate https://bugreports.qt.io/browse/QTMCU-62?focusedCommentId=582707&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-582707

Issue A:

• When a kit using the ARMGCC toolchain is created, it shows without warnings in the Kit manager. If the user restarts Qt creator, it shows with a warning and "No debugger set up"

Issue B:

•  When a kit using the IAR toolchain is created, it always shows with the warning: "No compiler set up"

Issue C:

• Even if the IAR compiler issue is fixed, this kit still shows the warning "No debugger set up".

Cause:

1. The kit manager expects every kit to have a debugger associated, otherwise the warning is shown.
2. When a kit with ARMGCC is created, armgdb is registered as a new debugger. However, when leaving QtCreator this is not saved. On restart, the debugger information has been lost and thus the kit has no debugger associated.
3. With IAR, there is a function for registering the debugger which is never called. A special condition skips that ("if IAR then skip").

Possible ways to address the issues:

A) The reason why armgdb is not saved is because the registration code is missing the debugger type, and it defaults to "No Debugger". The saving function skips it. The solution would be to set the type to "GdbEngineType".

B) The code that recognises the IAR compiler attemps to run the executable and extract information from it. The issue could be that the hardcoded information about how to run it and parse the output is outdated in relation to newer versions of the compiler. This still needs to be investigated. Currently the situation is that no compiler is detected, and thus none is registered.

C) According to dawsliwa , there must not be any debugger support for any of the MCU platforms. However, there is code for offering that support (armgdb for ARMGCC and CSpyBat for IAR).  If that is correct, we have several options:

• C.1) Remove the code for registering MCU debuggers, and modify QtCreator's Kit manager so that it does skip the check for debuggers in the case of MCU kits.
• C.2) Remove the code, and document clearly that these warnings are to be expected in the UI and ignored by the customers (and our QA team).
• C.3) Re-enable assigning a debugger to IAR kits, and fix any issues uncovered with the detection of CSpyBat.
• C.4) Other?

Acceptance criteria

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