Deprecate @DurationFormat and related classes

[philwebb]

If spring-projects/spring-framework#30396 is merged we can deprecate our own implementation (assuming they are compatible).

[wilkinsona]

The Framework PR was merged in 6.2. Should we look at deprecating our support in 3.5 so we can remove it in 4.0?

[philwebb]

We're going to try and get this into the GA

[mhalbritter]

In our configuration properties, we use @DurationUnit(ChronoUnit.SECONDS), which sets the default duration unit.

When migrating to Framework's annotations there's no thing as a @DurationUnit annotation. The next best thing is @DurationFormat(style = Style.SIMPLE, defaultUnit = Unit.SECONDS), but this forces us to set a style. @DurationUnit(ChronoUnit.SECONDS) auto-detects simple and ISO8601, which @DurationFormat(style = Style.SIMPLE, defaultUnit = Unit.SECONDS) doesn't. Unfortunately there's no Style.AUTODETECT in framework.