Rename Oriya to Odia, and more

Rename Oriya to Odia, and more

Due to "The Orissa (Alteration of Name) Act, 2011"
(https://legislative.gov.in/sites/default/files/A2011-15.pdf)
Oriya has been renamed to Odia.

* lisp/language/indian.el (set-language-info-alist): Rename
Oriya to Odia.  Improve Oriya composition rules.
* lisp/leim/quail/indian.el ("odia"): New input method.
* lisp/erc/erc-lang.el: Obsolete the iso-638-languages variable
(which was a typo) and replace it with iso-639-1-languages.

* etc/HELLO: Rename Oriya to Odia.
Replace the old Odia greeting with the new one.
Add a Hindi greeting separate from the Devanagari one.
(Bug#55493)