McuSupport: Show Info in case of unconfigures Qt for MCUs target Kits

When installing Qt for MCUs via the SDK installer, the user (in many cases first-time evaluator) has to create the kits for Qt for MCUs. For those who see Qt Creator for the first time, it is difficult to find out where to search for the UI that generates those kits.

Let's help the user with an InfoBar entry that in case of...

• McuSupport plugin enabled (by SDK installer)
• Settings key [McuSupport]/Package_QtForMCUsSdk set (by SDK installer)
• Absence of valid Qt for MCUs Kits

... helps to directly open the right page and tab of the Options dialog.