### _Why are the changes needed?_
This PR covers #1619.
Overall, this PR contains the following changs,
1. change `build/dist` script to support flink sql engine
2. enhance `externals/flink-sql-engine/pom.xml` to support create a shaded jar
3. simplify `externals/kyuubi-flink-sql-engine/bin/flink-sql-engine.sh`
4. introduce `FlinkSQLEngine`(flink sql engine entrypoint) and `FlinkProcessBuilder`(kyuubi server launcher)
5. add ut in kyuubi server side
After this PR, we can run the basic query e.g. `select now()` from beeline and get result, and Kyuubi Server can auto launch flink engine if there is no proper one. The Flink engine also supports other engine share levels defined in Kyuubi.
The implementation based on Flink 1.14 codebase.
### _How was this patch tested?_
- [ ] Add some test cases that check the changes thoroughly including negative and positive cases if possible
- [ ] Add screenshots for manual tests if appropriate
- [x] [Run test](https://kyuubi.readthedocs.io/en/latest/develop_tools/testing.html#running-tests) locally before make a pull request
Closes#1629 from pan3793/flink-backend.
Closes#1629
b7e5f0e3 [Cheng Pan] revert tgz name change
a4496c37 [Cheng Pan] Fix reflection
3b4e86a1 [Cheng Pan] deps
68efa42c [Cheng Pan] log
8a9e37f3 [Cheng Pan] nit
10fb2bc3 [Cheng Pan] CI
c1560fdb [Cheng Pan] nit
303e2f1e [Cheng Pan] Restore log conf
d84720b1 [Cheng Pan] SessionContext
b258d81a [Cheng Pan] cleanup
16edd528 [Cheng Pan] Cleanup
9ae54557 [Cheng Pan] Fix CI
25b6b57d [Cheng Pan] hadoop-client-api
c12b5ca4 [Cheng Pan] Server UT pass
502d3f08 [Cheng Pan] pass
dac4323b [yanghua] Laungh local flink engine container successfully
Lead-authored-by: Cheng Pan <chengpan@apache.org>
Co-authored-by: yanghua <yanghua1127@gmail.com>
Signed-off-by: Kent Yao <yao@apache.org>
cb8721fef1