This feature is propsoed in [DSIP-1](https://cwiki.apache.org/confluence/display/DORIS/DSIP-001%3A+Java+UDF).
This PR support fixed-length input and output Java UDF. Phase I in DIP-1 is done after this PR.
To support Java UDF effeciently, I use no data copy in JNI call and all compute operations are off-heap in Java.
To achieve that, I use a UdfExecutor instead.
For users, a UDF class must have a public evaluate method.
This CL mainly changes:
1. Add star schema benchmark tools in `tools/ssb-tools`, for user to easy load and test with SSB data set.
2. Disable the segment cache for some read scenario such as compaction and alter operation.(Fix#6924 )
3. Fix a bug that `max_segment_num_per_rowset` won't work(Fix#6926)
4. Enable `enable_batch_delete_by_default` by default.
It will crash when there are External engine tables in doris after executing "python show_segment_status.py"
The main reason is external engine tables don't have any index and partitions. So it should be ignored.
1. Disable the MySQL client and LZO library by default when building the Doris.
MySQL client library is used for MySQL external table feature.
This feature will be replaced by the new ODBC external table soon.
LZO library is used to compress/decompress data of some old data format of Doris,
which is no longer used anymore.
2. Add missing license to some files.
3. For all non-Apache-License code, all are explained in NOTICE file and the corresponding license is declared.
4. Remove the js source code from webroot, it will be downloaded as thirdparty
This CL mainly made the following modifications:
1. Reorganized SegmentV2 upgrade document.
2. When the variable `use_v2_rollup` is set to true, the base rollup in v2 format is forcibly queried for verifying the data.
3. Fix a problem that there is no persistent storage format information in the schema change operation that performs v2 conversion.
4. Allow users to directly create v2 format tables.
