internal/chartconfig: add collection for gopls/gotoolchain

Measure the types of GOTOOLCHAIN values used with gopls to help
understand what fraction of users work in environments where toolchain
upgrades are supported.

Fixes golang/go#68771

Change-Id: I306ee93f6d992d7f0fcd6b41ecf36bbc3724b81b
Reviewed-on: https://go-review.googlesource.com/c/telemetry/+/603857
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Commit-Queue: Hongxiang Jiang <hxjiang@golang.org>
Auto-Submit: Robert Findley <rfindley@google.com>
Auto-Submit: Hongxiang Jiang <hxjiang@golang.org>
Reviewed-by: Hongxiang Jiang <hxjiang@golang.org>

config/config.json

@@ -622,6 +622,10 @@
 				{
 					"Name": "crash/no-running-goroutine",
 					"Rate": 1
+				},
+				{
+					"Name": "gopls/gotoolchain:{auto,path,local,other}",
+					"Rate": 1
 				}
 			],
 			"Stacks": [

internal/chartconfig/config.txt

@@ -138,3 +138,11 @@ description: measure distribution of failed govulncheck internal assumptions
 type: partition
 issue: https://go.dev/issue/67678
 program: golang.org/x/vuln/cmd/govulncheck
+---
+counter: gopls/gotoolchain:{auto,path,local,other}
+title: GOTOOLCHAIN types used with gopls
+description: measure the types of GOTOOLCHAIN values used with gopls
+type: partition
+issue: https://go.dev/issue/68771
+program: golang.org/x/tools/gopls
+version: v0.16.0