Simplify `to_dict` / `from_dict` implementation in Bedrock components

[julian-risch]

Given that the Amazon Bedrock integration requires Haystack version >=2.23.0 since we merged PR #2783, we can benefit from the changes made to the default (de-)serialization of components in Haystack's default_from_dict and default_to_dict.

For example, we should no longer need to explicitly call deserialize_secrets_inplace.

For more context, see deepset-ai/haystack#9206 and as example of the kind of code changes we expect: https://github.com/deepset-ai/haystack/pull/10411/changes