Update or assign label in SET clause

**Is your feature request related to a problem? Please describe.**
Label cannot be set using `SET a:NewLabel`.

**Describe the solution you'd like**
The above syntax should update label, or assign label if no label exsits.

**Describe alternatives you've considered**
I am not aware of any functions that can update labels. So, I believe there is no alternative to this issue. If there is one and the new syntax seems less important, then this issue can be closed.

**Additional context**
N/A