Ensure jetty api servlets/filters take precedence over webdefault.xml declarations.

[janbartel]

Jetty version(s)
12.0.x

Jetty Environment
ee8, ee9, ee10

During the investigations for #10652 it was discovered that a DefaultServlet and JettyJspServlet - defined and mapped to / and *.jsp respectively via the jetty api - lead to duplicate mappings when combined with the declarations in webdefault.xml.

For example, given the jetty code:

WebAppContext webapp = new WebAppContext();
webapp.getServletHandler().addServletWithMapping(DefaultServlet.class.getName(), "/");
webapp.getServletHandler().addServletWithMapping(MySpecialJspServlet.class.getName(), "*.jsp");

and the contents of webdefault.xml being:

  <servlet>
    <servlet-name>default</servlet-name>
    <servlet-class>org.eclipse.jetty.ee10.servlet.DefaultServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>default</servlet-name>
    <url-pattern>/</url-pattern>
  </servlet-mapping>

  <servlet id="jsp">
    <servlet-name>jsp</servlet-name>
    <servlet-class>org.eclipse.jetty.ee10.jsp.JettyJspServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>jsp</servlet-name>
    <url-pattern>*.jsp</url-pattern>
    <url-pattern>*.jspf</url-pattern>
    <url-pattern>*.jspx</url-pattern>
    <url-pattern>*.xsp</url-pattern>
    <url-pattern>*.JSP</url-pattern>
    <url-pattern>*.JSPF</url-pattern>
    <url-pattern>*.JSPX</url-pattern>
    <url-pattern>*.XSP</url-pattern>
  </servlet-mapping>

the result is 2 different DefaultServlet instances both mapped to / and 2 different jsp servlets, both mapped to *.jsp:

|     |  |  |  +> servlets oeje10s.ServletHandler@55ab5a0b{STARTED} size=4
|     |  |  |  |  +> org.eclipse.jetty.ee10.servlet.DefaultServlet-ad72ea0==org.eclipse.jetty.ee10.servlet.DefaultServlet@252bd084
|     |  |  |  |  +> MySpecialJspServlet-26dae73f==MySpecialJspServlet@5e45d115
|     |  |  |  |  +> default==org.eclipse.jetty.ee10.servlet.DefaultServlet@5c13d641
|     |  |  |  |  +> jsp==org.eclipse.jetty.ee10.jsp.JettyJspServlet@19c47
|     |  |  |  +> servletMappings oeje10s.ServletHandler@55ab5a0b{STARTED} size=4
|     |  |  |  |  +> [/]=>org.eclipse.jetty.ee10.servlet.DefaultServlet-ad72ea0
|     |  |  |  |  +> [*.jsp]=>MySpecialJspServlet-26dae73f
|     |  |  |  |  +> [/]=>default
|     |  |  |  |  +> [*.jsp, *.jspf, *.jspx, *.xsp, *.JSP, *.JSPF, *.JSPX, *.XSP]=>jsp

[janbartel]

Fixed via #10668