QDoc: Ensure CMD_TARGET behavior is consistent both inside and outside paragraphs

QTBUG-70959 exposes an issue with CMD_KEYWORD, a command that shares a large degree of its code with that of CMD_TARGET, where behavior inside and outside paragraphs is inconsistent. The fix for that issue exposed some questions related to CMD_TARGET that should be considered and addressed. From the review;

This should more generally touch anything that uses getRestOfLine in a tail parsing-position. Most of them already use leavePara in the same way (we should really ask if it is acceptable that this has to be done manually for each such command which has shown to be error-prone) but cases such as CMD_SINCELIST and CMD_INPUT do not seem to have the same safe-guarding. We should consider and test-for the whole group for that bug and not only CMD_TARGET.

This issue is a reminder such that this work is completed promptly.