kcms/keys: Port RowLayout to QQC2.SplitView (and other things)

Fix up import aliases

Add or change them to something consistent, and sort alphabetically.

Remove an extra trailing whitespace

Turn a readonly property into an id reference

Indirect access is not needed here

Add tooltip to the component name, port others to attached properties

Port RowLayout to QQC2.SplitView

Gives users an opportunity to resize the columns, e.g. to see the full app name instead of an elided one.

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kinda requires qqc2-desktop-style to override a SplitView.qml with a Kirigami.Separator as a handle component A nearly native SplitView implementation is incoming: frameworks/qqc2-desktop-style!416 (merged)