feat: 增加MySQL数据库支持

[wan92hen]

1. 增加 MySQL 数据库部署支持
2. 调整默认 Halo 镜像版本

None

[wan92hen]

/hold

[wan92hen]

- 更新 Halo 版本到 v2.6.1
- 增加 MySQL 数据库部署支持
- 增加检测数据库连通性的初始化容器

[wan92hen]

/unhold

[JohnNiang]

Test steps:

gh repo clone halo-sigs/charts && cd charts
gh pr checkout 5
helm dependency build charts/halo
helm install halo -n halo charts/halo --create-namespace --set mysql.enabled=true --set postgresql.enabled=false
kubectl port-forward -n halo service/halo --address localhost 8090:http

Check the info of Halo:

{
  "git": {
    "branch": "HEAD",
    "commit": {
      "id": "15433b5",
      "time": "2023-06-14T10:20:14Z"
    }
  },
  "build": {
    "artifact": "application",
    "name": "application",
    "time": "2023-06-14T10:33:11.814Z",
    "version": "2.6.1",
    "group": "run.halo.app"
  },
  "java": {
    "version": "17.0.7",
    "vendor": {
      "name": "Eclipse Adoptium",
      "version": "Temurin-17.0.7+7"
    },
    "runtime": {
      "name": "OpenJDK Runtime Environment",
      "version": "17.0.7+7"
    },
    "jvm": {
      "name": "OpenJDK 64-Bit Server VM",
      "vendor": "Eclipse Adoptium",
      "version": "17.0.7+7"
    }
  },
  "os": {
    "name": "Linux",
    "version": "5.15.49-linuxkit-pr",
    "arch": "aarch64"
  },
  "database": {
    "name": "Source distribution",
    "version": "8.0.33"
  }
}

It works very well, but I left some comments below, please take a look at them.

[guqing]

/lgtm

[JohnNiang]

/approve

[f2c-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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