[llvm-nm] Fix handling of symbol types 't' 'd' 'r'

This restores part of r359311 that was reverted by r359830.

Rewrite the symbol types to fix several issues.

Notable difference is that the type of __init_array_start changes from
't' to 'd'.

GNU nm used to mark ELF symbols relative to .init_array as 't'
https://sourceware.org/bugzilla/show_bug.cgi?id=24505 (before 2.33)
because ".init" is the prefix. The bug was copied by r287803.

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D61551

llvm-svn: 360339