Bug in GDBJIT feature implementation: NotifyGDB not always called.

[0xfk0]

I think i have found a bug in GDBJIT feature: function NotifyGdb::MethodPrepared not always called. Sometimes methods of managed code might be compiled without notifying GDB of that.

GDB is notified about method compilation in MethodDesc::PrepareInitialCode (prestub.cpp:325):

 324 #if defined(FEATURE_GDBJIT) && defined(TARGET_UNIX) && !defined(CROSSGEN_COMPILE)
 325     NotifyGdb::MethodPrepared(this);
 326 #endif

But in a few cases MethodDesc::PrepareCode is called directly (without call to PrepareInitialCode), so GDB stay not notified about the changes. Such cases are following:

1. TieredCompilationManager::CompileCodeVersion (tieredcompilation.cpp:780) directly callse PrepareCode;
2. JitPatchpointWorker (jithelpers.cpp:5055);
3. CodeVersionManager::PublishVersionableCodeIfNecessary (codeversion.cpp:1702);
4. MulticoreJitProfilePlayer::CompileMethodDesc (multicorejitplayer.cpp:548).

So, I think there is a bug exists: call to NotifyGdb::MethodPrepared() should be moved from function MethodDesc::PrepareInitialCode to the function ``MethodDesc::PrepareCode`.

[0xfk0]

@alpencolt, @gbalykov, @y-yamshchikov