Refactor to new framework (#98)

- Adjust directory structure
```text
├── internal
│   ├── app
│   │   ├── artifactcache
│   │   ├── cmd
│   │   ├── poll
│   │   └── run
│   └── pkg
│       ├── client
│       ├── config
│       ├── envcheck
│       ├── labels
│       ├── report
│       └── ver
└── main.go
```
- New pkg `labels` to parse label
- New pkg `report` to report logs to Gitea
- Remove pkg `engine`, use `envcheck` to check if docker running.
- Rewrite `runtime` to `run`
- Rewrite `poller` to `poll`
- Simplify some code and remove what's useless.

Reviewed-on: https://gitea.com/gitea/act_runner/pulls/98
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Jason Song <i@wolfogre.com>
Co-committed-by: Jason Song <i@wolfogre.com>

internal/pkg/envcheck/docker.go

@@ -0,0 +1,27 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package envcheck
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/docker/docker/client"
+)
+
+func CheckIfDockerRunning(ctx context.Context) error {
+	// TODO: if runner support configures to use docker, we need config.Config to pass in
+	cli, err := client.NewClientWithOpts(client.FromEnv)
+	if err != nil {
+		return err
+	}
+	defer cli.Close()
+
+	_, err = cli.Ping(ctx)
+	if err != nil {
+		return fmt.Errorf("cannot ping the docker daemon, does it running? %w", err)
+	}
+
+	return nil
+}