del centos 6

[TD-10815]<fix>: MODIFY COLUMN:'invalid operation: invalid column name', -2147483136

[TD-10813]<fix>: DROP COLUMN:'invalid operation: invalid column name', -2147483136

[TD-10897]<fix>: SchemaLess : Schemaless will auto convert Convert uppercase letters to lowercase

[TD-6452]<feature>: taoskeeper metrics collector phase 1 taosd implementation

[TS-676]<fix>: fixed coredump when 'group by' was used

[TS-636]<fix>:escape % with \ suport

insert datas contains multiple timestamp columns, but this tool transfer it to 'char' and pops up errors. (#8634)

* insert datas contains multiple timestamp columns, but this tool transfer it to 'char' and pops up errors.

* insert datas contains multiple timestamp columns, but this tool transfer it to 'char' and pops up errors.

* insert datas contains multiple timestamp columns, but this tool transfer it to 'char' and pops up errors.

[TS-561][TS-646]<test>: add test case

Test/td 10871 d

Release/ver 2.3.2.0

[TS-672]<doc>: update c sample code url for stmt

[td-10748]interp

Feature/d8

Feature/d7

merge from master into develop

merge from 2.0 into master

[TD-10965]<fix>:schemaless: some record can't write into TDengine by schemaless

[TD-10998]<fix>: set default JSON string type to nchar

because bug5903 has some error, comment  this case