[opt](log) refactor the log dir config (#32933)

Refactor the config for log dir of FE and BE

TLDR:
- Use env variable `LOG_DIR` to set root log dir
- Remove `sys_log_dir` for FE and BE

Details:

1. FE

    1. The root log dir is set by env variable `LOG_DIR` in `fe.conf`
    2. The default value of `audit_log_dir` is same as `${LOG_DIR}/`
    3. The default value of `spark_launcher_log_dir` is `${LOG_DIR}/spark_launcher_log`
    4. The default value of `nereids_trace_log_dir` is `${LOG_DIR}/nereids_trace_log`
    5. The origin `sys_log_dir` is deprecated, and default value is `""`.
        But for compatibility, if user already set `sys_log_dir` before, Doris will still use it as root log dir.

2. BE

     1. The root log dir is set by env variable `LOG_DIR` in `be.conf`
     2. Remove `pipeline_tracing_log_dir`, use `${LOG_DIR}` directly.
     3. The origin `sys_log_dir` is deprecated, and default value is `""`.
         But for compatibility, if user already set `sys_log_dir` before, Doris will still use it as root log dir.

fe/fe-common/src/main/java/org/apache/doris/common/Config.java

@@ -62,9 +62,10 @@ public class Config extends ConfigBase {
      * sys_log_enable_compress:
      *      default is false. if true, will compress fe.log & fe.warn.log by gzip
      */
+    @Deprecated // use env var LOG_DIR instead
     @ConfField(description = {"FE 日志文件的存放路径，用于存放 fe.log。",
             "The path of the FE log file, used to store fe.log"})
-    public static String sys_log_dir = System.getenv("DORIS_HOME") + "/log";
+    public static String sys_log_dir = "";
 
     @ConfField(description = {"FE 日志的级别", "The level of FE log"}, options = {"INFO", "WARN", "ERROR", "FATAL"})
     public static String sys_log_level = "INFO";
@@ -101,7 +102,7 @@ public class Config extends ConfigBase {
 
     @ConfField(description = {"FE 审计日志文件的存放路径，用于存放 fe.audit.log。",
             "The path of the FE audit log file, used to store fe.audit.log"})
-    public static String audit_log_dir = System.getenv("DORIS_HOME") + "/log";
+    public static String audit_log_dir = System.getenv("LOG_DIR");
     @ConfField(description = {"FE 审计日志文件的最大数量。超过这个数量后，最老的日志文件会被删除",
             "The maximum number of FE audit log files. "
                     + "After exceeding this number, the oldest log file will be deleted"})
@@ -570,7 +571,7 @@ public class Config extends ConfigBase {
     public static String spark_resource_path = "";
 
     @ConfField(description = {"Spark launcher 日志路径", "Spark launcher log dir"})
-    public static String spark_launcher_log_dir = sys_log_dir + "/spark_launcher_log";
+    public static String spark_launcher_log_dir = System.getenv("LOG_DIR") + "/spark_launcher_log";
 
     @ConfField(description = {"Yarn client 的路径", "Yarn client path"})
     public static String yarn_client_path = System.getenv("DORIS_HOME") + "/lib/yarn-client/hadoop/bin/yarn";
@@ -2468,7 +2469,7 @@ public class Config extends ConfigBase {
 
     @ConfField(description = {"nereids trace文件的存放路径。",
             "The path of the nereids trace file."})
-    public static String nereids_trace_log_dir = System.getenv("DORIS_HOME") + "/log/nereids_trace";
+    public static String nereids_trace_log_dir = System.getenv("LOG_DIR") + "/nereids_trace";
 
     @ConfField(mutable = true, masterOnly = true, description = {
             "备份过程中，分配给每个be的upload任务最大个数，默认值为3个。",

fe/fe-common/src/main/java/org/apache/doris/common/io/DiskUtils.java

@@ -44,7 +44,6 @@ public class DiskUtils {
             return df;
         }
 
-
         Process process;
         try {
             process = Runtime.getRuntime().exec("df -k " + dir);