[lldb] CommandObjectMemoryFind: Improve epxression evaluation error messages

We now bubble up the expression evaluation diagnostics to the user and
also distinguish between "expression failed to parse/run" versus other
ways in which expressions didn't complete (e.g., setup errors, etc.).

Before:
```
(lldb) memory find -e "" 0x16fdfedc0 0x16fdfede0
error: expression evaluation failed. pass a string instead
(lldb) memory find -e "invalid" 0x16fdfedc0 0x16fdfede0
error: expression evaluation failed. pass a string instead
```

After:
```
(lldb) memory find -e "" 0x16fdfedc0 0x16fdfede0
error: Expression evaluation failed:
error: No result returned from expression. Exit status: 1
(lldb) memory find -e "invalid" 0x16fdfedc0 0x16fdfede0
error: Expression evaluation failed:
error: <user expression 0>:1:1: use of undeclared identifier 'invalid'
    1 | invalid
      | ^~~~~~~
```

Author: Michael137

lldb/source/Commands/CommandObjectMemory.cpp

@@ -925,9 +925,12 @@ EvaluateExpression(llvm::StringRef expression, StackFrame &frame,
   ValueObjectSP result_sp;
   auto status =
       process.GetTarget().EvaluateExpression(expression, &frame, result_sp);
-  if (status != eExpressionCompleted || !result_sp)
+  if (!result_sp)
     return llvm::createStringError(
-        "expression evaluation failed. pass a string instead");
+        "No result returned from expression. Exit status: %d", status);
+
+  if (status != eExpressionCompleted)
+    return result_sp->GetError().ToError();
 
   result_sp = result_sp->GetQualifiedRepresentationIfAvailable(
       result_sp->GetDynamicValueType(), /*synthValue=*/true);
@@ -1082,6 +1085,7 @@ class CommandObjectMemoryFind : public CommandObjectParsed {
           m_memory_options.m_expr.GetValueAs<llvm::StringRef>().value_or(""),
           m_exe_ctx.GetFrameRef(), *process);
       if (!result_or_err) {
+        result.AppendError("Expression evaluation failed: ");
         result.AppendError(llvm::toString(result_or_err.takeError()));
         return;
       }

lldb/test/API/functionalities/memory/find/TestMemoryFind.py

@@ -56,10 +56,23 @@ def test_memory_find(self):
         # Invalid expr is an error.
         self.expect(
             'memory find -e "not_a_symbol" `&bytedata[0]` `&bytedata[15]`',
+            substrs=[
+                "Expression evaluation failed:",
+                "use of undeclared identifier 'not_a_symbol'",
+            ],
+            error=True,
+        )
+
+        self.expect(
+            'memory find -e "" `&bytedata[0]` `&bytedata[2]`',
+            substrs=[
+                "Expression evaluation failed:",
+                "No result returned from expression. Exit status: 1",
+            ],
             error=True,
-            substrs=["error: expression evaluation failed. pass a string instead"],
         )
 
+        # Valid expressions/strings
         self.expect(
             'memory find -e "(uint8_t)0x22" `&bytedata[0]` `&bytedata[15]`',
             substrs=["data found at location: 0x", "22 33 44 55 66"],