Make new command for creating blockages

[rovinski]

Create a new top-level command, perhaps in the ord namespace, which allows for easier creation of blockages.

Is there any direct command to place blockages in specific coordinates, If no whats the way do that. I have referred to plcement_blockages.tcl in scripts, In that odb::dbBlockage_create is used

Originally posted by @GundraHarshini in https://github.com/The-OpenROAD-Project/OpenROAD/discussions/6429