elf: Move elf note parsing to ObjectFileELF.cpp

Separate ELF note implementations were introduced for core files and
GNU build-id.  Move the more general one from elf-core to ObjectFileELF
and use it for build-id as well.

Review: http://llvm-reviews.chandlerc.com/D1902


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@196125 91177308-0d34-0410-b5e6-96231b3b80d8