Bump java version from 8 to 11

[dr0i]

Resolves #343.

Consumes the rc from metafacture-core which also uses java 11.
(See metafacture/metafacture-core#515).

[blackwinter]

I don't think we should mix:

1. Bumping the Java version,
2. Updating the metafacture-core dependency, and
3. Increasing the metafacture-fix version number.

This pull request is about 1. only.

Also, some tests (unit and integration) need to be updated. (Fixed in db9745b; see also 3d8d0e5.)

[blackwinter]

Produces warnings:

• EqualsVerifier:

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by nl.jqno.equalsverifier.internal.reflection.FieldModifier (file:/data/gradle/caches/modules-2/files-2.1/nl.jqno.equalsverifier/equalsverifier/3.8.2/1af9cb8854f510e42ddbcd6570212ed485a0315a/equalsverifier-3.8.2.jar) to field java.util.regex.IntHashSet.entries
WARNING: Please consider reporting this to the maintainers of nl.jqno.equalsverifier.internal.reflection.FieldModifier
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
OpenJDK 64-Bit Server VM warning: Sharing is only supported for boot loader classes because bootstrap classpath has been appended
OpenJDK 64-Bit Server VM warning: Sharing is only supported for boot loader classes because bootstrap classpath has been appended

• Mockito:

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.mockito.internal.util.reflection.AccessibilityChanger (file:/data/gradle/caches/modules-2/files-2.1/org.mockito/mockito-core/2.27.0/835fc3283b481f4758b8ef464cd560c649c08b00/mockito-core-2.27.0.jar) to field java.lang.Enum.name
WARNING: Please consider reporting this to the maintainers of org.mockito.internal.util.reflection.AccessibilityChanger
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

[blackwinter]

Thanks!

Since the illegal reflective access warnings are still occurring with the latest versions of EqualsVerifier (3.15.8) and Mockito (5.2.0), we might ignore them for now.