[Imporve][Fake-Connector-V2]support user-defined-schmea and random data for fake-table

[laglangyue]

Purpose of this pull request

the connector-v2-fake did't not support enough data type, and not quickly to modify，more time we need the fake to test the dataType Mapper，
so I do these works：
(1) optimization connector-fake-v2 so that we can easy to add column name,type and data
(2) change the spark example for connector-fake-v2，and fix some dead Http link in this example conf file
(3) I find the method don't contain the condition SqlType=NULL： org.apache.seatunnel.translation.serialization.RowConverter#validate，I don't sure it OK。and the SqlType of VOID_TYPE is NULL
(4) the error message is bad in org.apache.seatunnel.translation.serialization.RowConverter(line 60), i fix it

Check list

• Code changed are covered with tests, or it does not need tests for reason:
• If any new Jar binary package adding in your PR, please add License Notice according
  New License Guide
• If necessary, please update the documentation to describe the new feature. https://github.com/apache/incubator-seatunnel/tree/dev/docs

[laglangyue]

I find SeatunnelSchema that it not implement Serializable, it Example-task will error.
I add it.

[laglangyue]

the PR has completed. I add Junit5-test and test random data correctly.
For some complex types, example-v2-spark may occur some exceptions, but they are not the reason for Fake-V2, and during the spark type conversion process. I will test and try to repair them in another PR, because there are too many in this PR

[hailin0]

Can you add the connectors-v2/FakeSource docs?

[hailin0]

Can you add the connectors-v2/FakeSource docs?

here https://github.com/apache/incubator-seatunnel/tree/dev/docs/en/connector-v2/source

[laglangyue]

Can you add the connectors-v2/FakeSource docs?

yes , I update the config to keep the schema parameters consistent such as LocalFile and HDFS source.
Thank you for your guidance. This is my first contribution in Github.

[hailin0]

LGTM
@CalvinKirs