Enable call hierarchy implementors

[gayanper]

Fixes #2780

[gayanper]

@rgrunber WDYT ?

• Should we add a new preference for this ?
• Do we need any UI indication like adding some prefix to the symbol name or details ?

[gayanper]

@jdneo @rgrunber @jjohnstn @testforstephen What do you think ?

[gayanper]

@jdneo @rgrunber @jjohnstn @testforstephen @snjeza Any feedback ?

[rgrunber]

Any comments on #2780 (comment) ?

[rgrunber]

Ok, assuming we're fine with the workflow there's just one case I don't understand.

If I perform an outgoing call hierarchy on fetchName(int) (from the example) I see the following, once I expeand get(int) : E - java.util.List

Is this claiming that java.util.Vector's get(int) (at the bottom) declaration has an outgoing call to contains(Object) because I don't see that when I look into the get(int) declaration.

Also, if I perform outgoing call hierarchy directly on java.util.List's get(int) I don't see any of the above entries. Is this intended ?

[rgrunber]

@gayanper , this should be fine to merge. Just curious about the questions I had in the comment above.