Debug information: fix encoding of source code locations

Slicer was emitting DBG_ADVANCE_LINE for source locations, which
is not a correct interpretation of the .dex specification (so the
tools consuming .dex debug information did not get the right information)

The fix is to use the "special opcodes" to emit source locations
(and use DBG_ADVANCE_LINE when the line delta is out of range for
the special opcodes)

Bug: 37240685

Test: bazel test :dexter_tests

Change-Id: I05c2c5c38e3f1f4fceb1d4053dfe2762eb53c16d