[Bug] Fix ClassCastException (#4833)

[ccoffline]

Proposed changes

fix to #4833

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• [] 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)
• [] Code refactor (Modify the code structure, format the code, etc...)

Checklist

• I have create an issue on (Fix #ISSUE), and have described the bug/feature there in detail
• Compiling and unit tests pass locally with my changes
• [] I have added tests that prove my fix is effective or that my feature works
• [] If this change need a document change, I have updated the document
• Any dependent changes have been merged

Further comments

[morningman]

I think if the predicate like substr(dt, 7, 8) in ('09'), we should not do the partition prunner.
So here:
https://github.com/apache/incubator-doris/blob/f40868a4805f0ba503bcca9a9c04f704b61c121b/fe/fe-core/src/main/java/org/apache/doris/planner/SingleNodePlanner.java#L958-L972

We should check if inPredicate.getChild(0) is not a slotRef, do not create partition filter for it.
So it won't goes to the compareLiteral() logic.

[ccoffline]

@morningman I think cast CastExpr to LiteralExpr will definitely cause an exception.
I just don't know whether getResultValue() will solve that though I didn't see anything wrong in the test.
https://github.com/apache/incubator-doris/blob/b1c1ffda4a0d5ff2f0be4f9d2f25997a31537ea8/fe/fe-core/src/main/java/org/apache/doris/catalog/PartitionKey.java#L135-L150
I'm not fully understand the logic in partition pruner. Maybe it should be in another PR=.=