[lldb] Load the fblldb module automatically

Summary:
```
// Facebook only:
// We want to load automatically the fblldb python module as soon as lldb or
// lldb-vscode start. This will ensure that logging and formatters are enabled
// by default.
//
// As we want to have a mechanism for not triggering this by default, if the
// user is starting lldb disabling .lldbinit support, then we also don't load
// this module. This is equivalent to appending this line to all .lldbinit
// files.
//
// We don't have the fblldb module on windows, so we don't include it for that
// build.
```

Test Plan:
the fbsymbols module is loaded automatically

```
./bin/lldb
(lldb) help fbsymbols
Facebook {mini,core}dump utility.  Expects 'raw' input (see 'help raw-input'.)
```

Reviewers: wanyi

Reviewed By: wanyi

Subscribers: mnovakovic, serhiyr, phabricatorlinter

Differential Revision: https://phabricator.intern.facebook.com/D29372804

Tags: accept2ship

Signature: 29372804:1624567770:07836e50e576bd809124ed80a6bc01082190e48f

[lldb] Load fblldbinit instead of fblldb

Summary: Once accepted, it'll merge it with the existing commit in our branch so that we keep the commit list as short as possible.

Test Plan: https://www.internalfb.com/diff/D30293094

Reviewers: aadsm, wanyi

Reviewed By: aadsm

Subscribers: mnovakovic, serhiyr

Differential Revision: https://phabricator.intern.facebook.com/D30293211

Tags: accept2ship

Signature: 30293211:1628880953:423e2e543cade107df69da0ebf458e581e54ae3a

lldb/source/Interpreter/CommandInterpreter.cpp

@@ -2352,6 +2352,20 @@ void CommandInterpreter::SourceInitFileHome(CommandReturnObject &result,
     result.SetStatus(eReturnStatusSuccessFinishNoResult);
     return;
   }
+#if !defined(_WIN32)
+  // Facebook only:
+  //
+  // The 'fblldbinit' module will set up the python support specific to FB.
+  //
+  // As we want to have a mechanism for not triggering this by default, if the
+  // user is starting lldb disabling .lldbinit support, then we also don't load
+  // this module. This is equivalent to preppending the following line to all
+  // .lldbinit files.
+  //
+  // We don't have the fblldbinit module on windows, so we don't include it for
+  // that build.
+  HandleCommand("script import fblldbinit", eLazyBoolNo, result);
+#endif
 
   llvm::SmallString<128> init_file;