Adopt Framework's HttpMessageConverters

[snicoll]

A recent change in Spring Framework 7.0 snapshots deprecated messageConverters(List).

I believe the intention of this customizer is to only add the configured converters and, if they aren't any, then let the standard behavior of registering default converters from framework.

As noted by the deprecation note, we should use configureMessageConverters(Builder) instead. However, using this method seems to register the default irrespective of us providing some converters.

I've suppressed the warning for now in 0efe9c2 as we need to figure out if a change in framework and/or boot is required.

[bclozel]

I'm repurposing this issue to overall adopt Framework's HttpMessageConverters in our codebase. We already suppressed warnings in aae3df0 and we have our own variant of HttpMessageConverters already.

We should:

• ensure that both suppress warnings are gone
• figure out what to do with our own HttpMessageConverters
• overall adapt our auto-configuration to those Framework changes