[lldb/DWARF] Ignore debug info pointing to the low addresses

specifically, ignore addresses that point before the first code section.

This resurrects D87172 with several notable changes:
- it fixes a bug where the early exits in InitializeObject left
  m_first_code_address "initialized" to LLDB_INVALID_ADDRESS (0xfff..f),
  which caused _everything_ to be ignored.
- it extends the line table fix to function parsing as well, where it
  replaces a similar check which was checking the executable permissions
  of the section. This was insufficient because some
  position-independent elf executables can have an executable segment
  mapped at file address zero. (What makes this fix different is that it
  checks for the executable-ness of the sections contained within that
  segment, and those will not be at address zero.)
- It uses a different test case, with an elf file with near-zero
  addresses, and checks for both line table and function parsing.

Differential Revision: https://reviews.llvm.org/D112058