www/lua-resty-session3: port sticking to version 3

This is based upon www/lua-resty-session (v4), but is needed for
lua-resty-openidc.

The version 3.x is pinned in the lua-resty-openidc dependencies:

https://github.com/zmartzone/lua-resty-openidc/blob/9f3a4fcade930f6f38ee0cb43cabf50cebffbcc9/lua-resty-openidc-1.7.6-3.rockspec#L27

There is apparently currently no clear plan on when/if lua-resty-openidc
will be updated to include changes for lua-resty-session 4.X, see
discussions on

https://github.com/zmartzone/lua-resty-openidc/issues/480

Additionally to what the author submitted some changes by me:

• add conflicts with www/lua-resty-session
• give up maintainership of www/lua-resty-session

PR: 281142