Ohara: [Manager] Tweak the same name warning message if users attempt to create a connector, stream or topic where its name is already taken

[konekoya]

• [x] 0.9 (#4137)
• [x] 0.10 (#4136)

[konekoya]

/cc @vitojeng @saivirtue and @oharastream/frontend

[saivirtue]

Thanks @konekoya ! ❤️

[vitojeng]

Thanks @konekoya !
This could reduce the user misunderstanding. It would be better back port to 0.9.x, if not, also ok. ping @chia7712 WDYT?

[chia7712]

+1 to backport

[konekoya]

As per our discssion, we will only tweak the warning message (via snackbar) so it better tells users why they cannot add a same name connector/stream/topic into the pipeline. And I will update the description.

/cc @oharastream/frontend