[lldb] Break out long help for 'frame var'

[kastiglione]

Summary

The current help for frame variable is somewhat long. Its length, combined with the few aliases (var, v, and vo) can make the output of apropos redundant and noisy.

This separates out the details into a separate long help.

[JDevlieghere]

Neat. LGTM

lldb/source/Commands/CommandObjectFrame.cpp

 // List images with associated information
 class CommandObjectFrameVariable : public CommandObjectParsed {
 public:
   CommandObjectFrameVariable(CommandInterpreter &interpreter)
       : CommandObjectParsed(
             interpreter, "frame variable",
             "Show variables for the current stack frame. Defaults to all "
             "arguments and local variables in scope. Names of argument, "
-            "local, file static and file global variables can be specified. "
-            "Children of aggregate variables can be specified such as "
-            "'var->child.x'.  The -> and [] operators in 'frame variable' do "
-            "not invoke operator overloads if they exist, but directly access "
-            "the specified element.  If you want to trigger operator overloads "
-            "use the expression command to print the variable instead."
-            "\nIt is worth noting that except for overloaded "
-            "operators, when printing local variables 'expr local_var' and "
-            "'frame var local_var' produce the same "
-            "results.  However, 'frame variable' is more efficient, since it "
-            "uses debug information and memory reads directly, rather than "
-            "parsing and evaluating an expression, which may even involve "
-            "JITing and running code in the target program.",
+            "local, file static and file global variables can be specified.",
             nullptr,
             eCommandRequiresFrame | eCommandTryTargetAPILock |
                 eCommandProcessMustBeLaunched | eCommandProcessMustBePaused |
                 eCommandRequiresProcess),
         m_option_group(),
         m_option_variable(
             true), // Include the frame specific options by passing "true"
         m_option_format(eFormatDefault), m_varobj_options() {
+    SetHelpLong(R"(
+Children of aggregate variables can be specified such as 'var->child.x'.  In
+'frame variable', the operators -> and [] do not invoke operator overloads if
+they exist, but directly access the specified element.  If you want to trigger
+operator overloads use the expression command to print the variable instead.
+
+It is worth noting that except for overloaded operators, when printing local
+variables 'expr local_var' and 'frame var local_var' produce the same results.
+However, 'frame variable' is more efficient, since it uses debug information and
+memory reads directly, rather than parsing and evaluating an expression, which
+may even involve JITing and running code in the target program.)");
+
     CommandArgumentEntry arg;
     CommandArgumentData var_name_arg;
 
     // Define the first (and only) variant of this arg.
     var_name_arg.arg_type = eArgTypeVarName;
     var_name_arg.arg_repetition = eArgRepeatStar;
 
     // There is only one variant this argument could be; put it into the