Support MariaDB Native Driver (#2787)

#### What type of PR is this?
/kind improvement


#### What this PR does / why we need it:
引入对R2DBC的MariaDB的支持，增加例子配置

#### Special notes for your reviewer:
现在，Halo可以使用MariaDB数据库原生驱动了，摆脱MySQL驱动带来的连接问题。

- [x] 支持首次启动执行SQL脚本创建表

#### Does this PR introduce a user-facing change?

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```release-note
支持 MariaDB 数据库连接
```

build.gradle

@@ -92,6 +92,7 @@ dependencies {
     // for more.
     runtimeOnly 'io.r2dbc:r2dbc-h2'
     runtimeOnly 'com.github.jasync-sql:jasync-r2dbc-mysql:2.1.7'
+    runtimeOnly 'org.mariadb:r2dbc-mariadb:1.1.3'
     runtimeOnly 'org.postgresql:postgresql'
     runtimeOnly 'org.postgresql:r2dbc-postgresql'
 

src/main/resources/application-mariadb.yaml

@@ -0,0 +1,9 @@
+spring:
+  r2dbc:
+    url: r2dbc:pool:mariadb://localhost:3306/halo
+    username: root
+    password: mariadb
+  sql:
+    init:
+      mode: always
+      platform: mysql