Update copyright headers to use "<year>-present" pattern

[sbrannen]

Historically, we have used <introduction year>-<modification year> as the pattern for copyright headers.

For example: Copyright 2002-2025 the original author or authors.

However, we have been encouraged to use present as the modification year.

In light of that, we should update the following to enforce the new pattern.

• [ ] The patterns in our SpringHeaderCheck Checkstyle rules
• [ ] The update_copyright_headers.sh script
• [ ] The Copyright 2002-${year} template in org.eclipse.jdt.ui.prefs

We should then run update_copyright_headers.sh to modify all source files.