[flagd-provider] fix non-conformant config options

[toddbaert]

Currently the flagd provider doesn't default to unlimited retries, and doesn't throw immediately if it can't start.

See: https://github.com/open-feature/flagd/blob/main/docs/other_resources/creating_providers.md#environment-variables and https://github.com/open-feature/flagd/blob/main/docs/other_resources/creating_providers.md#provider-lifecycle-initialization-and-shutdown

Definition of done:

• update the flagd provider to default to 0 (infinite) retries
• verify other defaults
• reject immediately if the provider cannot connect, but continue to try to connect