[CALCITE-6343] Fix AS alias operator stripping MEASUREness from measures

[barrkel]

When inferring the return type of an operator application, don't unwrap MEASURE types if the operator is an AS alias.

[YiwenWu]

test failed：

[barrkel]

I saw a failure with SqlXmlFunctionsTest which doesn't reproduce in the IDE and looks to be completely unrelated to my change, so I'm not sure what's going on there.

[sonarqubecloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
90.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[mihaibudiu]

This looks easy to fix, if you can handle the checker errors we could merge this in time for 1.38