[gdb/testsuite] Add gdb.base/wrap-line.exp

Add a test-case that tests prompt edit wrapping in CLI, both
for TERM=xterm and TERM=ansi, both with auto-detected and hard-coded width.

In the TERM=ansi case with auto-detected width we run into PR cli/30346, so
add a KFAIL for that failure mode.

Tested on x86_64-linux.