Reimplement kubectl plugin release workflow (#8812)

* Feat: reimplement kubectl plugin release system

This commit does the following changes:
- Add GitHub Actions pipeline for releasing the plugin
- Removes the build/build-plugin.sh and replaces this with GoReleaser
- Adds the use of krew-release-bot for automatically updating the krew
  release
- Removes the make target for build/build-plugin.sh

Signed-off-by: Ismayil Mirzali <ismayilmirzeli@gmail.com>

* Fix: pin github actions stages with commit sha

Signed-off-by: Ismayil Mirzali <ismayilmirzeli@gmail.com>

Signed-off-by: Ismayil Mirzali <ismayilmirzeli@gmail.com>

.github/workflows/plugin.yaml

@@ -0,0 +1,37 @@
+name: kubectl plugin
+
+on:
+  push:
+    branches:
+      - "main"
+    paths:
+      - "cmd/plugin/**"
+    tags:
+      - "v*"
+
+jobs:
+  release-plugin:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@2541b1294d2704b0964813337f33b291d3f8596b # v3.0.2
+        with:
+          fetch-depth: 0
+
+      - name: Set up Go
+        uses: actions/setup-go@b22fbbc2921299758641fab08929b4ac52b32923 # v3.2.0
+        with:
+          go-version: 1.18
+
+      - name: Run GoReleaser
+        uses: goreleaser/goreleaser-action@68acf3b1adf004ac9c2f0a4259e85c5f66e99bef # v3.0.0
+        with:
+          version: latest
+          args: release --rm-dist
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Update new version in krew-index
+        uses: rajatjindal/krew-release-bot@92da038bbf995803124a8e50ebd438b2f37bbbb0 # v0.0.43
+        with:
+          krew_template_file: cmd/plugin/krew.yaml