Introduce LDBG_OS() macro as a variant of LDBG() (#157194)

Also, improve LDBG() to accept debug type and level in any order, and
add unit-tests for LDBG() and LGDB_OS().

LDBG_OS() is a macro that behaves like LDBG() but instead of directly
using it to stream the output, it takes a callback function that will be
called with a raw_ostream.

Co-authored-by: Andrzej Warzyński <andrzej.warzynski@gmail.com>
GitOrigin-RevId: c84f34bcd8c7fb6d5038b3f52da8c7be64ad5189