Remove support for generating .eh_frame ELF section.

The eh_frame support was originally added because the
old libunwind library didn't support debug_frame.
The new libunwind supports debug_frame well, and since
we have switched to it, we can remove the legacy code.

The main advantage of debug_frame is that it can be
compressed as part of mini-debug-info.

I am somewhat preserving the .eh_frame_hdr binary
search table (renamed as .debug_frame_hdr.android).

Bug: 123621350
Test: Generated framework oat files are identical.
Change-Id: I35b18895482f2176e02df07b086af7a1d40f90d5