[chore] Upgrade our Go version to 1.22 (#2862)

* [chore] Upgrade our Go version to 1.22

With Go 1.22 having been released at the start of February, it's now
been a few months. No major issues have shown up, and the two point
release since then have primarily been security fixes plus some general
bug fixing.

This sets the required Go version to 1.22, as there's nothing in 1.22.1
or 1.22.2 that we would explicitly require. It sets the toolchain to the
latest point release, to ensure we pick up any fixes from there when
building releases etc.

* [chore] Update CI to Go 1.22

* [chore] Update golangci-lint to 1.25.7

Newer version should know about Go 1.22 and run fine.

* [chore] Update Docker container to Go 1.22

* [chore] Update Dockerfile to newer Alpine version

* sign drone.yml

* add missing license header

---------

Co-authored-by: tobi <tobi.smethurst@protonmail.com>

internal/oauth/util.go

@@ -1,3 +1,20 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
 package oauth
 
 import (