make the case-sensitive works on the whole dispatchers configuration

[3AceShowHand]

Is your feature request related to a problem?

At the moment, there is one configuration named as case-sensitive, which controls the database name and table name specified in the dispatcher part.

Let's take the following as an example, the columns specified the columns used to calculate the partition.

It may be hard for the user to specify columns with case if there are a lot of tables. For example, table's may have different columns name to indicate the same thing, such as ID, Id, id, etc.

[sink]
dispatchers = [
    {matcher = ['test2.*'], partition = "columns", columns = ["id", "a"]},
]

This should also takes effect on the column-selector configurations

[sink]
column-selectors = [
    {matcher = ['test.t1'], columns = ['a', 'b']},
    {matcher = ['test.*'], columns = ["*", "!b"]},
    {matcher = ['test1.t1'], columns = ['column*', '!column1']},
    {matcher = ['test3.t'], columns = ["column?", "!column1"]},
]

Describe the feature you'd like

the case-sensitive field, should also take affect on the columns configurations.

Describe alternatives you've considered

No response

Teachability, Documentation, Adoption, Migration Strategy

After this feature is implemented, should also update the document to mention this.

[wk989898]

case-sensitive should control the database names and tables but not the columns.
Relevant docs:

1. https://docs.pingcap.com/tidb/stable/mysql-compatibility/#:~:text=lower_case_table_names
2. https://dev.mysql.com/doc/refman/5.7/en/identifier-case-sensitivity.html