build: Use Go 1.22, minimum is Go 1.21 (#9408)

Also updated dependencies, and an adjustment to build tags for how those
are handled and how irrelevant go1.15 is nowadays...

.github/workflows/build-infra-dockers.yaml

@@ -7,7 +7,7 @@ on:
       - infra-*
 
 env:
-  GO_VERSION: "~1.21.5"
+  GO_VERSION: "~1.22.0"
   CGO_ENABLED: "0"
   BUILD_USER: docker
   BUILD_HOST: github.syncthing.net

.github/workflows/build-syncthing.yaml

@@ -12,7 +12,7 @@ env:
   # The go version to use for builds. We set check-latest to true when
   # installing, so we get the latest patch version that matches the
   # expression.
-  GO_VERSION: "~1.21.5"
+  GO_VERSION: "~1.22.0"
 
   # Optimize compatibility on the slow archictures.
   GO386: softfloat
@@ -48,7 +48,7 @@ jobs:
         runner: ["windows-latest", "ubuntu-latest", "macos-latest"]
         # The oldest version in this list should match what we have in our go.mod.
         # Variables don't seem to be supported here, or we could have done something nice.
-        go: ["~1.20.12", "~1.21.5"]
+        go: ["~1.21.7", "~1.22.0"]
     runs-on: ${{ matrix.runner }}
     steps:
       - name: Set git to use LF

.github/workflows/update-docs-translations.yaml

@@ -16,7 +16,7 @@ jobs:
           token: ${{ secrets.ACTIONS_GITHUB_TOKEN }}
       - uses: actions/setup-go@v5
         with:
-          go-version: ^1.19.6
+          go-version: stable
       - run: |
           set -euo pipefail
           git config --global user.name 'Syncthing Release Automation'