feat(provider): instantiate recommended fillers by default

[yash-atreya]

Motivation

Instantiate RecommendedFillers by default.

Solution

• RecommededFillers are added when the ProviderBuilder is instantiated using new() i.e ProviderBuilder::new() will now return FillProvider with the recommended fillers instantiated.
• Users can opt-out of this behaviour using .disable_recommended_fillers().

For example, if a user want just wants cached_nonce_management. It can be achieved like so:

let provider = ProviderBuilder::new()
            .disable_recommended_fillers()
            .with_cached_nonce_management()
            .on_anvil();

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

[yash-atreya]

@gakonst @mattsse bump for review

[mattsse]

lgtm!