[lldb] Unify CalculateMD5 return types (#90921)

# Overview
In my previous PR: https://github.com/llvm/llvm-project/pull/88812,
@JDevlieghere suggested to match return types of the various calculate
md5 functions.

This PR achieves that by changing the various calculate md5 functions to
return `llvm::ErrorOr<llvm::MD5::MD5Result>`.
 
The suggestion was to go for `std::optional<>` but I opted for
`llvm::ErrorOr<>` because local calculate md5 was already possibly
returning `ErrorOr`.

To make sure I didn't break the md5 calculation functionality, I ran
some tests for the gdb remote client, and things seem to work.

# Testing
1. Remote file doesn't exist

![image](https://github.com/llvm/llvm-project/assets/1326275/b26859e2-18c3-4685-be8f-c6b6a5a4bc77)

1. Remote file differs

![image](https://github.com/llvm/llvm-project/assets/1326275/cbdb3c58-555a-401b-9444-c5ff4c04c491)

1. Remote file matches

![image](https://github.com/llvm/llvm-project/assets/1326275/07561572-22d1-4e0a-988f-bc91b5c2ffce)

## Test gaps
Unfortunately, I had to modify
`lldb/source/Plugins/Platform/MacOSX/PlatformDarwinDevice.cpp` and I
can't test the changes there. Hopefully, the existing test suite / code
review from whomever is reading this will catch any issues.

Co-authored-by: Anthony Ha <antha@microsoft.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/lldb/source/Target/RemoteAwarePlatform.cpp b/lldb/source/Target/RemoteAwarePlatform.cpp
index 0bd6c9251c85..9a41a423cadd 100644
--- a/lldb/source/Target/RemoteAwarePlatform.cpp
+++ b/lldb/source/Target/RemoteAwarePlatform.cpp
@@ -266,11 +266,11 @@ Status RemoteAwarePlatform::Unlink(const FileSpec &file_spec) {
   return Platform::Unlink(file_spec);
 }
 
-bool RemoteAwarePlatform::CalculateMD5(const FileSpec &file_spec, uint64_t &low,
-                                       uint64_t &high) {
+llvm::ErrorOr<llvm::MD5::MD5Result>
+RemoteAwarePlatform::CalculateMD5(const FileSpec &file_spec) {
   if (m_remote_platform_sp)
-    return m_remote_platform_sp->CalculateMD5(file_spec, low, high);
-  return Platform::CalculateMD5(file_spec, low, high);
+    return m_remote_platform_sp->CalculateMD5(file_spec);
+  return Platform::CalculateMD5(file_spec);
 }
 
 FileSpec RemoteAwarePlatform::GetRemoteWorkingDirectory() {