[llvm-objcopy][NFC] More error cleanup

Summary:
This removes calls to `error()`/`reportError()` in the main driver (llvm-objcopy.cpp) as well as the associated argv-parsing (CopyConfig.cpp). `logAllUnhandledErrors()` is now the main way to print errors.

There are still a few uses from within the per-arch drivers, so we can't delete them yet... but almost!

Reviewers: jhenderson, alexshap, espindola

Reviewed By: jhenderson

Subscribers: emaste, arichardson, jakehehrlich, jdoerfert, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D58316

llvm-svn: 354600
diff --git a/llvm/test/tools/llvm-objcopy/ELF/bad-output-format.test b/llvm/test/tools/llvm-objcopy/ELF/bad-output-format.test
index e01d955..f190a16 100644
--- a/llvm/test/tools/llvm-objcopy/ELF/bad-output-format.test
+++ b/llvm/test/tools/llvm-objcopy/ELF/bad-output-format.test
@@ -10,4 +10,4 @@
   Type:            ET_EXEC
   Machine:         EM_386
 
-# BAD-OUTPUT-FORMAT: Invalid output format: 'xyz'.
+# BAD-OUTPUT-FORMAT: Invalid output format: 'xyz'