AXIS2-6105 Remove Eclipse and IntelliJ IDEA plugins

Remove axis2-eclipse-codegen-plugin, axis2-eclipse-service-plugin,
and axis2-idea-plugin modules. These plugins are unmaintained, broken
on current Eclipse versions, and no longer used by the community per
the dev@ mailing list discussion.

Removes:
- 3 module directories (source and Eclipse PDE metadata)
- org.eclipse.platform dependencies (SWT, JFace, OSGi, Equinox)
- com.intellij:openapi and com.intellij:extensions dependencies
- intellij.version property
- Eclipse/IDEA entries from toc.xml, contents.xml.vm, tools/index.xml
- Download links from download.md.vm
- Eclipse-specific entries from src-assembly.xml, apidocs/pom.xml
- dist.py release script (Eclipse/IDEA plugin specific)
- modules/tool/build.xml and readme.txt (Eclipse-only build instructions)
- .gitignore entries for Eclipse plugin PDE artifacts
- Site docs: tools/eclipse/, tools/idea/

Retains: org.eclipse.angus (Jakarta mail), org.eclipse.jetty (test
transport), eclipse-settings-maven-plugin (code formatting) — these
are unrelated to the IDE plugins.