Require Java 11

[katzyn]

Additional changes:

1. Dependencies are updated.
2. Maven (and Maven Wrapper) are updated, because old versions don't support Java 11.
3. package.html files are replaced with package-info.java.
4. Anonymous TLS is removed, because it doesn't work anyway (H2's anonymous TLS does not work on Java 11 #1303).
5. Some classes from org.h2.dev.util package are removed, because they have better equivalents in modern versions of Java.
6. JDBC metadata now announces JDBC 4.3 compatibility.
7. Java 8 is excluded from CI matrix. (We can add Java 21 instead of it in the future).
8. Multi-release code for Java 9 and 10 is merged into the main code and new Java features are used in few places.