openapi: Add 'operationId' attribute to endpoints.
openapi: Add 'operationId' attribute to endpoints.

'operationId' helps code generators in naming functions and other purposes.
So name operationId of endpoints as their function names in python-zulip-api
if it exists else use most appropriate function name.

Part of #14100 .

rht/zulip,showell/zulip,andersk/zulip,brainwane/zulip,shubhamdhama/zulip,showell/zulip,zulip/zulip,rht/zulip,eeshangarg/zulip,timabbott/zulip,eeshangarg/zulip,shubhamdhama/zulip,timabbott/zulip,rht/zulip,zulip/zulip,zulip/zulip,brainwane/zulip,timabbott/zulip,rht/zulip,punchagan/zulip,synicalsyntax/zulip,eeshangarg/zulip,showell/zulip,zulip/zulip,synicalsyntax/zulip,andersk/zulip,kou/zulip,timabbott/zulip,zulip/zulip,shubhamdhama/zulip,brainwane/zulip,timabbott/zulip,zulip/zulip,andersk/zulip,showell/zulip,showell/zulip,andersk/zulip,timabbott/zulip,andersk/zulip,kou/zulip,synicalsyntax/zulip,eeshangarg/zulip,shubhamdhama/zulip,rht/zulip,punchagan/zulip,showell/zulip,hackerkid/zulip,punchagan/zulip,shubhamdhama/zulip,kou/zulip,brainwane/zulip,punchagan/zulip,punchagan/zulip,punchagan/zulip,timabbott/zulip,hackerkid/zulip,eeshangarg/zulip,eeshangarg/zulip,brainwane/zulip,hackerkid/zulip,synicalsyntax/zulip,kou/zulip,eeshangarg/zulip,synicalsyntax/zulip,kou/zulip,andersk/zulip,shubhamdhama/zulip,punchagan/zulip,shubhamdhama/zulip,brainwane/zulip,kou/zulip,hackerkid/zulip,hackerkid/zulip,synicalsyntax/zulip,andersk/zulip,hackerkid/zulip,synicalsyntax/zulip,kou/zulip,showell/zulip,rht/zulip,hackerkid/zulip,brainwane/zulip,zulip/zulip,rht/zulip