[Bug]Fix some schema change not work right
This CL mainly fix some schema change to varchar type not work right
because forget to logic check && Add ConvertTypeResolver to add
supported convert type in order to avoid forget logic check
This CL mainly changes:
1. Reorganized the code logic to limit the supported json format to two, and the import behavior is more consistent.
2. Modified the statistical behavior of the number of error rows when loading in json format, so that the error rows can be counted correctly.
3. See `load-json-format.md` to get details of loading json format.
Currently we choose BE random without check disk is available,
the create table will failed until create tablet task is sent to BE
and BE will check is there has available capacity to create tablet.
So check backend disk available by storage medium will reduce unnecessary RPC call.
