refactor(3p/gerrit-queue): use go:embed, bump go1.16, drop shell.nix

Previously, gerrit-queue used statik to embed files. Since go1.16, we
have go:embed, which solves this much nicer, without any requirements to
have the statik binary around.

As the only other thing the shell.nix and .envrc plumbing did was bring
a version of Go in scope, it's dropped now. We assume to have a
recent-enough go binary around, else go will complain.

Imported from https://github.com/flokli/gerrit-queue/pull/9

Change-Id: I851b06777a29d4f2d955cf3a7db6455a7189bc46
Reviewed-on: https://cl.tvl.fyi/c/depot/+/4329
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>
Autosubmit: tazjin <mail@tazj.in>

third_party/gerrit-queue/frontend/templates/changeset.tmpl.html

@@ -0,0 +1,15 @@
+{{ define "changeset" }}
+<tr>
+    <td>{{ .OwnerName }}</td>
+    <td>
+    <strong>{{ .Subject }}</strong> (<a href="{{ changesetURL . }}" target="_blank">#{{ .Number }}</a>)<br />
+    <small><code>{{ .CommitID }}</code></small>
+    </td>
+    <td>
+    <span>
+        {{ if .IsVerified }}<span class="badge badge-success badge-pill">+1 (CI)</span>{{ end }}
+        {{ if .IsCodeReviewed }}<span class="badge badge-info badge-pill">+2 (CR)</span>{{ end }}
+    </span>
+    </td>
+</tr>
+{{ end }}