defaults: set nostartofline

Having the cursor change column can be surprising.

Force startofline in functional and old tests.
Remove the functional breakindent test, as it's a subset of the oldtest one.

src/nvim/testdir/setup.vim

@@ -19,6 +19,7 @@ set sidescroll=0
 set tags=./tags,tags
 set undodir^=.
 set wildoptions=
+set startofline
 
 " Prevent Nvim log from writing to stderr.
 let $NVIM_LOG_FILE = exists($NVIM_LOG_FILE) ? $NVIM_LOG_FILE : 'Xnvim.log'