By implementing BTLR support in
SwTextFrame::SwitchVerticalToHorizontal() (Point version).

Cursor traveling now looks good: all of up/down/left/right direction
have the correct paragraph and character position for all the lrtb, tbrl
and btlr cases.

As a side effect this also fixes mouse click, where clicking above the
paragraph positioned the cursor at the bottom of the paragraph.

Explicitly add a test for the mouse case as well, given that I initially
planned to fix the keyboard part directly in SwCursor::UpDown(), where
the keyboard test would pass, but not the mouse one.

Change-Id: Iabeded3f03a64416cfcaf58e0438c4a1a793e662
Reviewed-on: https://gerrit.libreoffice.org/68886
Tested-by: Jenkins
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>