What changes were proposed in this pull request?

problem

This PR refactor how clickhosue backend supports wrting merge tree. When spark.sql.caseSensitive is false,

Before this PRs, We convert column name to lower case , and save to disc, for example, given the following DDL

CREATE TABLE IF NOT EXISTS LINEITEM_MERGETREE_CASE_SENSITIVE
(
 L_ORDERKEY      bigint,
 L_PARTKEY       bigint,
 L_SUPPKEY       bigint,
 L_LINENUMBER    bigint,
 L_QUANTITY      double,
 L_EXTENDEDPRICE double,
 L_DISCOUNT      double,
 L_TAX           double,
 L_RETURNFLAG    string,
 L_LINESTATUS    string,
 L_SHIPDATE      date,
 L_COMMITDATE    date,
 L_RECEIPTDATE   date,
 L_SHIPINSTRUCT  string,
 L_SHIPMODE      string,
 L_COMMENT       string
)
USING clickhouse
PARTITIONED BY (L_SHIPDATE)
TBLPROPERTIES (orderByKey='L_DISCOUNT')
LOCATION '$basePath/LINEITEM_MERGETREE_CASE_SENSITIVE

Here are columns.txt

spark.sql.caseSensitive is a configuarion, once it is set to true，unless user force the column name to be lowercase
in the sql, subsequent operations will fail, even if the column name is capitalized as declared by the user.

change

I did two chagne:

1. We don't convert user defined column name, but the index column name, for example, minmax, partition name, etc. will be normailized to user defined column name
2. Add a rename transformer if needed when read from merge tree.

(Fixes: #7028)

How was this patch tested?

Reopen ignored UTs