This commit fixes missing descriptions and default values when
applicable for `management.server.ssl`, `server.compression`,
`server.http2`, `server.servlet.jsp`, `server.servlet.session` and
`server.ssl`.

Those nested namespace are managed by a POJO that is declared outside
of the module of the target @ConfigurationProperties type using it. As
a result, the annotation processor has no access to the source model and
can't extract the description and the default value, if any.

This commit migrates the misleading field-level Javadoc to manual meta
data for the time being.

Closes gh-14669