Bump Servlet API / JSTL

[slominskir]

We bumped Java EE 8 to Jakarta EE 10 but missed the web.xml servlet version and also JSTL URIs. Apps appear to work fine, as apparently Wildfly handles older version declaration and older JSTL URIs, but these probably need to be updated.

Update web.xml with:

<web-app version="6.0"
         xmlns="https://jakarta.ee/xml/ns/jakartaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="https://jakarta.ee/xml/ns/jakartaee https://jakarta.ee/xml/ns/jakartaee/web-app_6_0.xsd">

Search and replace JSP taglib URI with:
http://java.sun.com/jsp/jstl/ -> jakarta.tags.

[slominskir]

Few notes:

It turns out IntelliJ won't recognize the jakarta.tags URIs and will mark errors everywhere unless you explicitly declare a dependency on a JSTL implementation. This seems like a bug / counter to whole point of separating API vs Impl, but whatever. Wildfly provides an implementation, though I can't immediately see what it is poking around in the modules directory. It doesn't really matter, so we're simply declaring a dependency on the glassfish impl, as compileOnly / provided. That makes IntelliJ happy.

Wildlfly doesn't really care if we're declaring Servlet version 4 or 6 in web.xml and also works with either old or new JSTL tag URIs. So this issue isn't exactly a bug, but going forward Jakarta EE apps should probably be using new declarations and presumably Wildfly will stop being backwards compatible at some point. The fact Widlfly is backwards compatible is why I didn't catch this earlier, it works either way.