[BUG] Error occurred in DefaultStreamLoader#getAvailableHost while trying to load a URL due to configuration issues.

[xumanbu]

When configuring the load URL value, I mistakenly used a comma instead of a semicolon, like this : 10.x.x.1:8030,10.x.x.2:8030,10.x.x.3:8030.

except: throw an exception while flink start failed
acture: only log error, flink application is running available

I found two point can be optimized.

1. DefaultStreamLoader#testHttpConnection catched all Exception at now, wo can catch MalformedURLException and throw an IllegalArgumentException.
2. StarRocksSinkOptions#validateStreamLoadUrl should be enhance.

Failed to connect to address:http://10.x.x.1:8030,10.x.x.2:8030,10.x.x.3:8030
java.net.MalformedURLException: For input string: "8030,10.x.x.2:8030,10.x.x.3:8030"
	at java.net.URL.<init>(URL.java:645) ~[?:1.8.0_262]
	at java.net.URL.<init>(URL.java:508) ~[?:1.8.0_262]
	at java.net.URL.<init>(URL.java:457) ~[?:1.8.0_262]
	at com.starrocks.data.load.stream.DefaultStreamLoader.testHttpConnection(DefaultStreamLoader.java:302) ~[flink-connector-starrocks-2.5_flink-1.15.2-vip.jar:?]
	at com.starrocks.data.load.stream.DefaultStreamLoader.getAvailableHost(DefaultStreamLoader.java:290) ~[flink-connector-starrocks-2.5_flink-1.15.2-vip.jar:?]
	at com.starrocks.data.load.stream.DefaultStreamLoader.send(DefaultStreamLoader.java:225) ~[flink-connector-starrocks-2.5_flink-1.15.2-vip.jar:?]
	at com.starrocks.data.load.stream.DefaultStreamLoader.lambda$send$2(DefaultStreamLoader.java:113) ~[flink-connector-starrocks-2.5_flink-1.15.2-vip.jar:?]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_262]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:1.8.0_262]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:1.8.0_262]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_262]
Caused by: java.lang.NumberFormatException: For input string: "8030,gd17-bigdata-starrocks-120-179-42.idc.vip.com:8030,gd17-bigdata-starrocks-120-204-34.idc.vip.com:8030"
	at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65) ~[?:1.8.0_262]
	at java.lang.Integer.parseInt(Integer.java:580) ~[?:1.8.0_262]
	at java.lang.Integer.parseInt(Integer.java:615) ~[?:1.8.0_262]
	at java.net.URLStreamHandler.parseURL(URLStreamHandler.java:222) ~[?:1.8.0_262]
	at java.net.URL.<init>(URL.java:640) ~[?:1.8.0_262]
	... 10 more