Improve vtable handling

Version and Platform (required):

• Binary Ninja Version: 4.1.5747-dev Personal, 7558ffe9
• OS: manjaro
• CPU Architecture: x86_64

Bug Description:
There are a few improvements which could be made to the handling of vtables.

1. If I double click a vtable member with only one outgoing data reference it should open the referenced function.
   Currently it opens the type window instead.

2. If I click on a vtable member function it should show its callers as code references. At the moment I have to go back to the vtable in the data section to the get the callers.

Steps To Reproduce:

1. Double click a member of a vtable.

2. Check xrefs on a member of a vtable

Expected Behavior:

1. It opens the referenced function

2. The cross reference view is populated with the callers of the function as code references.

Screenshots:

1. Double click issue:
   

2. Xrefs not propagated
   

Additional Information:
Bndb and exe used.
CppTestBinja.zip

Start by opening the supplied CppTestBinja.zip reproduction in Binary Ninja and inspect the vtable member navigation and cross-reference behavior described in the issue. Verify both expected outcomes: a single outgoing data reference opens the referenced function, and callers appear as code references when viewing the vtable member. Done means both behaviors work for the provided reproduction.