Recommit r369190 "[llvm-readobj/llvm-readelf] - Improve/cleanup the error reporting...

Recommit r369190 "[llvm-readobj/llvm-readelf] - Improve/cleanup the error reporting API."

Fix: Add a `consumeError` call removed by mistake to 'printStackSize',
this should fix the "Expected<T> must be checked before access or destruction." reported by following bot:
http://lab.llvm.org:8011/builders/clang-x64-windows-msvc/builds/9743/steps/stage%201%20check/logs/stdio

Original commit message:
Currently we have the following functions for error reporting:

LLVM_ATTRIBUTE_NORETURN void reportError(Twine Msg);
void reportError(Error Err, StringRef Input);
void reportWarning(Twine Msg);
void reportWarning(StringRef Input, Error Err);
void warn(llvm::Error Err);
void error(std::error_code EC);

Problems are: naming is inconsistent, arguments order is inconsistent,
some of the functions looks excessive.

After applying this patch we have:

void reportError(Error Err, StringRef Input);
void reportError(std::error_code EC, StringRef Input);
void reportWarning(Error Err, StringRef Input);

I'd be happy to remove reportError(std::error_code EC, StringRef Input) too, but it
is used by COFF heavily.

Test cases were updated, they show an improvement introduced.

Differential revision: https://reviews.llvm.org/D66286

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@369194 91177308-0d34-0410-b5e6-96231b3b80d8