Make BedrockAwsConnectionProperties#region empty by default

[therepanic]

If our region is empty, then DefaultAwsRegionProviderChain will be used, which will search for the region in every possible way. This should be better for us, instead of setting the default field ourselves.

Resolves: #3223

[ilayaperumalg]

@therepanic Thanks for the PR! Could you update the documentation for the change (removing the default)?

[therepanic]

Thanks, @ilayaperumalg. Sorry, I accidentally formatted the wrong changes and closed the PR.

I changed the documentation of the region field (to make it clear that if it is empty, DefaultAwsRegionProviderChain will figure out which region to use).

Also, I have now specified the region in the tests to make the tests pass. Everything should be fine now.

[ilayaperumalg]

@therepanic No problem at all, thank you for the quick follow up!

[therepanic]

I forgot to use spring-javaformat:apply, run the build again please

[markpollack]

@ashakirin what do you think?

[tzolov]

Mind, that removing the default region is a breaking change. It has to come at 1.1.x

[ashakirin]

@markpollack, @tzolov: basically this change makes sense in combination with #823 fix, but it can break existing code based on fixed default region (Bedrock "us-east-1" has the most comprehensive model selection). Plan for next minor release?