debug: compound map keys cannot be expanded

[polinasok]

Code:

	mapWithCompoundValue := map[int]myStruct{123: {123}}
	mapWithCompoundKey := map[myStruct]int{{123}: 123}

UI:

Logs:

### Expand mapWithCompoundValue
VariablesResponse [
 {
  "name": "123",
  "value": "<main.myStruct>",
  "evaluateName": "mapWithCompoundValue[123]",
  "variablesReference": 1003 #### <============= this allows to expand again to view the value
 }
VariablesResponse [
 {
  "name": "i",
  "value": "123",
  "evaluateName": "mapWithCompoundValue.i",
  "variablesReference": 0
 }

### Expand mapWithConpoundKey
VariablesResponse [
 {
  "name": "<main.myStruct>",
  "value": "123",
  "evaluateName": "mapWithCompoundKey[<main.myStruct>]",
  "variablesReference": 0 #### <=============== no way to expand more to view the key
 }

[polinasok]

This is how new adapter in delve repo deals with this: go-delve/delve#2111 (comment)

[polinasok]

This has been fixed in new dlv-dap adapter.
Test fixtures in delve repo:
https://github.com/go-delve/delve/blob/2c1a822632776fa78b8ab23ac74fa0ea2fa1d7bf/_fixtures/testvariables2.go#L237
https://github.com/go-delve/delve/blob/2c1a822632776fa78b8ab23ac74fa0ea2fa1d7bf/_fixtures/testvariables2.go#L238
Unittests in delve repo:
https://github.com/go-delve/delve/blob/2c1a822632776fa78b8ab23ac74fa0ea2fa1d7bf/service/dap/server_test.go#L1173
https://github.com/go-delve/delve/blob/2c1a822632776fa78b8ab23ac74fa0ea2fa1d7bf/service/dap/server_test.go#L1198

[polinasok]

This is what the support looks like in dlv-dap: