KYLIN-5280 Introduce memcached as a distributed cache for queries for Kylin5

[zznlime]

Branch to commit

• [ ] Branch kylin3 for v2.x to v3.x
• [ ] Branch kylin4 for v4.x
• [x] Branch kylin5 for v5.x

Types of changes

What types of changes does your code introduce to Kylin? Put an x in the boxes that apply

• [ ] Bugfix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Documentation Update (if none of the other choices apply)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• [x] I have created an issue on Kylin's jira, and have described the bug/feature there in detail
• [x] Commit messages in my PR start with the related jira ID, like "KYLIN-5280 Introduce memcached as a distributed cache for queries for Kylin5"
• [x] Compiling and unit tests pass locally with my changes
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have added necessary documentation (if appropriate)
• [ ] Any dependent changes have been merged

[lgtm-com[bot]]

This pull request introduces 2 alerts when merging 8c21de7df630f2b4df488016ee3203c5e51ac040 into ab1f17f1e6b778b8f85d50ab1d282afc26d69f26 - view on LGTM.com

new alerts:

• 1 for Implicit conversion from array to string
• 1 for Boxed variable is never null

[hit-lacus]

After check, I have following commnets:

1. Looks like a lot of configuration entries is hard-coded in MemcachedCacheConfig, such as timeout, do they really not need be configured by kylin users?
2. Would you please add unit test for CompositeMemcachedCache? A good example is QueryRedisCacheTest. And I find a embedded-memcached in https://github.com/mwarc/embedded-memcached-spring.

@zznlime

[zznlime]

Thanks for the suggestions.

1. have added some configuration to KylinConfig, which can be configured by kylin users now.
2. have added a unit test for CompositeMemcachedCache with an embedded-memcached server.

@hit-lacus