Properties of type java.time.Year are not recognized in tests

Using dynamic finders for properties of java.time.Year type in test code results in `InvalidDataAccessResourceUsageException` - `Cannot query (...) on non-existent property: (...)`, while in regular code it works fine.

Debugging had shown that java.time.Year is not recognized as a simple type in [MappingFactory](https://github.com/grails/grails-data-mapping/blob/master/grails-datastore-core/src/main/groovy/org/grails/datastore/mapping/model/MappingFactory.java).

### Task List

- [x] Steps to reproduce provided
- [x] Stacktrace (if present) provided
- [x] Example that reproduces the problem uploaded to Github
- [x] Full description of the issue provided (see below)

### Steps to Reproduce

1. Create domain class with property of type java.time.Year (e.g. `year`)
2. In unit test use dynamic finder with the java.time.Year property (`findByYear()`)

### Expected Behaviour

Dynamic finder should work as in non-test code.

### Actual Behaviour

Using dynamic finder throws exception:

```Cannot query [sandbox.TestDomain] on non-existent property: year
org.springframework.dao.InvalidDataAccessResourceUsageException: Cannot query [sandbox.TestDomain] on non-existent property: year
at org.grails.datastore.mapping.simple.query.SimpleMapQuery.getValidProperty(SimpleMapQuery.groovy:751)
at org.grails.datastore.mapping.simple.query.SimpleMapQuery.executeSubQueryInternal(SimpleMapQuery.groovy:690)
at org.grails.datastore.mapping.simple.query.SimpleMapQuery.executeSubQuery(SimpleMapQuery.groovy:676)
at org.grails.datastore.mapping.simple.query.SimpleMapQuery.executeQuery(SimpleMapQuery.groovy:63)
at org.grails.datastore.mapping.query.Query.doList(Query.java:575)
at org.grails.datastore.mapping.query.Query.singleResult(Query.java:563)
at org.grails.datastore.gorm.finders.AbstractFindByFinder.invokeQuery(AbstractFindByFinder.java:35)
at org.grails.datastore.gorm.finders.AbstractFindByFinder$1.doInSession(AbstractFindByFinder.java:29)
at org.grails.datastore.mapping.core.DatastoreUtils.execute(DatastoreUtils.java:319)
at org.grails.datastore.gorm.finders.AbstractFinder.execute(AbstractFinder.java:42)
at org.grails.datastore.gorm.finders.AbstractFindByFinder.doInvokeInternal(AbstractFindByFinder.java:27)
at org.grails.datastore.gorm.finders.DynamicFinder.invoke(DynamicFinder.java:174)
at org.grails.datastore.gorm.finders.DynamicFinder.invoke(DynamicFinder.java:374)
at org.grails.datastore.gorm.GormStaticApi.methodMissing(GormStaticApi.groovy:173)
at org.grails.datastore.gorm.GormEntity$Trait$Helper.staticMethodMissing(GormEntity.groovy:749)
at sandbox.TestDomainSpec.Dynamic finder should work with java.time.Year(TestDomainSpec.groovy:16)
```

### Environment Information

- **Operating System**: Windows 10
- **GORM Version:** 6.0.9.RELEASE
- **Grails Version (if using Grails):** 3.2.8
- **JDK Version:** 1.8.0_131

### Example Application

GitHub repository: https://github.com/piotrgajow/Sandbox
Branch: `grails-JavaTimeYearPropertyIssue` - https://github.com/piotrgajow/Sandbox/tree/grails-JavaTimeYearPropertyIssue

Notable files:

[Domain class](https://github.com/piotrgajow/Sandbox/blob/grails-JavaTimeYearPropertyIssue/grails-3.2.8/sandbox/grails-app/domain/sandbox/TestDomain.groovy).
Finder working properly in [Bootstrap](https://github.com/piotrgajow/Sandbox/blob/grails-JavaTimeYearPropertyIssue/grails-3.2.8/sandbox/grails-app/init/sandbox/BootStrap.groovy).
Finder not working in [test code](https://github.com/piotrgajow/Sandbox/blob/grails-JavaTimeYearPropertyIssue/grails-3.2.8/sandbox/src/test/groovy/sandbox/TestDomainSpec.groovy).

Start with MappingFactory.java and reproduce the failure using the example application's TestDomain.groovy and TestDomainSpec.groovy. Compare the working finder in BootStrap.groovy with the failing test, then verify that findByYear() works for a java.time.Year property in test code without the non-existent-property exception.

Written by the indexing model from the issue text.