[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/compress-and-decompress-debug-sections-error.test b/llvm/test/tools/llvm-objcopy/ELF/compress-and-decompress-debug-sections-error.test
index 0866e20..aac9bb3 100644
--- a/llvm/test/tools/llvm-objcopy/ELF/compress-and-decompress-debug-sections-error.test
+++ b/llvm/test/tools/llvm-objcopy/ELF/compress-and-decompress-debug-sections-error.test
@@ -3,5 +3,5 @@
 # RUN: yaml2obj %p/Inputs/compress-debug-sections.yaml -o %t.o
 # RUN: not llvm-objcopy --compress-debug-sections=zlib --decompress-debug-sections %t.o 2>&1 | FileCheck %s
 
-# CHECK: Cannot specify --compress-debug-sections at the same time as --decompress-debug-sections at the same time.
+# CHECK: Cannot specify --compress-debug-sections at the same time as --decompress-debug-sections at the same time