Add -Region option to Add-GceManagedInstane cmdlets

[quoctruong]

This change is 

[quoctruong]

@ILMTitan PTAL. I modify the logic when pipelining the object so that:

1. If -Region is supplied, we will create a Regional Instance Group.
2. Otherwise, create a Zonal Instance Group. If the user supplies either -Project or -Zone parameters, we will use them instead of the default value from the SDK.

I have to add logic for this instead of using ParameterSet because I wasn't able to resolve them.

[ILMTitan]

I think the logic should be:

0. If the user specifies both -Zone and -Region, throw an error.
1. If the user specifies -Region, create a Region Instance Group there.
2. If the user specifies -Zone, create a Zone Instance Group there.
3. If the user supplies an object that specifies either Zone or Region, create that type of instance group.
4. Else create a Zone Instance Group at the default zone.

[quoctruong]

@ILMTitan Thanks for the great suggestion! PTAL.

[quoctruong]

@ILMTitan PTAL.

[quoctruong]

Thanks!