grafana-loki,promtail: 2.9.6 -> 3.0.0

Starting with v3.0.0, the ldflag prefix now also includes `v3`.

It's unclear if this will change with each major release.
This is something we should keep an eye on.

The commit right after this will add a simple version test for this
based on `testers.testVersion`.

https://github.com/grafana/loki/releases/tag/v3.0.0

changelog: https://github.com/grafana/loki/blob/c9142722684ad6aca2bb09ae5487d5a2af087d0f/CHANGELOG.md

diff (unusable, 5000+ edits because upstream vendors go deps): https://github.com/grafana/loki/compare/v2.9.6...v3.0.0

pkgs/servers/monitoring/loki/default.nix

@@ -8,14 +8,14 @@
 }:
 
 buildGoModule rec {
-  version = "2.9.6";
+  version = "3.0.0";
   pname = "grafana-loki";
 
   src = fetchFromGitHub {
     owner = "grafana";
     repo = "loki";
     rev = "v${version}";
-    hash = "sha256-79hK7axHf6soku5DvdXkE/0K4WKc4pnS9VMbVc1FS2I=";
+    hash = "sha256-2+OST6bKIjuhrXJKA+8vUERKT1/min7tN8oFxKn3L74=";
   };
 
   vendorHash = null;
@@ -40,7 +40,7 @@ buildGoModule rec {
 
   passthru.tests = { inherit (nixosTests) loki; };
 
-  ldflags = let t = "github.com/grafana/loki/pkg/util/build"; in [
+  ldflags = let t = "github.com/grafana/loki/v3/pkg/util/build"; in [
     "-s"
     "-w"
     "-X ${t}.Version=${version}"