LTTP: Rip Lttp specific entrance code out of core and use Region helpers

[alwaysintreble]

What is this fixing or adding?

some cleanup

How was this tested?

just unit tests. needs proper testing still

If this makes graphical changes, please attach screenshots.

[el-u]

Please revisit my feedback from #965, i.e.:

• implementing connect via super connect
• correct typing everywhere for addresses and target