Provide hover for "parent" segments of a reference address

[radeksimko]

Context

As part of #496 and hashicorp/hcl-lang#185 in particular, it was decided to treat any reference as immutable sequence of segments separated by dots.

For example, you will get the following data regardless of where exactly you hover over google_compute_instance.name.network_interface[0].network_ip:

Meaning that we always represent the whole address, or rather its very last segment.

Proposal

We could provide different hover data for different segments, for example:

• google_compute_instance.name - object
• google_compute_instance.name.network_interface - list of object
• google_compute_instance.name.network_interface[0] - object
• google_compute_instance.name.network_interface[0].network_ip - string (as before)