Avoid monitor contention inside MethodParameter.getParameterAnnotations()

[dukehoops-zz]

MethodParameter.getParameterAnnotations() calls
Method.getParameterAnnotations() on every invocation. Latter ends up
contending for a monitor inside (Sun) JDK code. Fix by caching values
returned by Method.getParameterAnnotations() in a static ConcurrentMap

Issue: SPR-9298

[dukehoops-zz]

FYI, I already submitted the CLA request

[cbeams]

Thanks, Nikita. This is now merged. The substance of your commit was pretty solid, but note that there were a number of changes necessary before actually committing:

• Reformatting of commit comment, including subject line, content of body and updating your Author: metadata
• Formatting of new static final fields
• Completing Javadoc for new #getMethodParameterAnnotations
• Updating Apache license header date ranges
• Consistent formatting of braces, e.g. opening { on same line, not newline; else { on newline instead of same line } else {
• Use of Spring's own Assert class instead of native Java assertions

Also, for any future pull requests, please submit from a topic branch with the same name as the JIRA issue, e.g. SPR-9298.

Most of the items above are covered in the contributor guidelines.