[FLINK-15933][catalog][doc] Update content of how generic table schem…

[lirui-apache]

…a is stored in hive via HiveCatalog

What is the purpose of the change

Update docs as a result of FLINK-15858.

Brief change log

• Add descriptions about hive v.s. generic table
• Move Supported Types to HiveCatalog page since it's more closely related
• Minor updates to the support of TIMESTAMP type

Verifying this change

NA

Does this pull request potentially affect one of the following parts:

NA

Documentation

NA

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Last check on commit 64fccf2 (Thu Feb 06 08:25:26 UTC 2020)

Warnings:

• Documentation files were touched, but no .zh.md files: Update Chinese documentation or file Jira ticket.

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[lirui-apache]

@bowenli86 @JingsongLi Let me know if you think the change makes sense. Thanks.

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[bowenli86]

LGTM, can you

1. update the example at https://ci.apache.org/projects/flink/flink-docs-master/dev/table/hive/hive_catalog.html#step-4-start-sql-client-and-create-a-kafka-table-with-flink-sql-ddl ? specifically the console output part of "DESCRIBE mykafka;"
2. update xxx.zh.md?

[lirui-apache]

@bowenli86 We don't have any console output for "DESCRIBE mykafka;" now. I'll add the output for "DESCRIBE FORMATTED mykafka;" instead.

[lirui-apache]

@bowenli86 Docs updated. Please have another look. Thanks.

[bowenli86]

@bowenli86 We don't have any console output for "DESCRIBE mykafka;" now. I'll add the output for "DESCRIBE FORMATTED mykafka;" instead.

why we don't have any console output for describing a table? Seems like a bug?

[lirui-apache]

@bowenli86 We don't have any console output for "DESCRIBE mykafka;" now. I'll add the output for "DESCRIBE FORMATTED mykafka;" instead.

why we don't have any console output for describing a table? Seems like a bug?

Because we have changed to store the generic table schema as properties. So from Hive perspective, the table doesn't have any columns.

[bowenli86]

@bowenli86 We don't have any console output for "DESCRIBE mykafka;" now. I'll add the output for "DESCRIBE FORMATTED mykafka;" instead.

why we don't have any console output for describing a table? Seems like a bug?

Because we have changed to store the generic table schema as properties. So from Hive perspective, the table doesn't have any columns.

my bad, I thought it's a flink cli...

LGTM, merging