[FEATURE] Init and Shutdown functions should take `context.Context` parameter

### Requirements

The StateHandler interface defines two functions: Init and Shutdown.
https://github.com/open-feature/go-sdk/blob/dd4cf71f8226026a71d51d1edcfd1026c965be15/openfeature/provider.go#L64-L67

There is also a top-level Shutdown function:
https://github.com/open-feature/go-sdk/blob/dd4cf71f8226026a71d51d1edcfd1026c965be15/openfeature/openfeature.go#L90-L92

[Section 2.4 of the specification](https://openfeature.dev/specification/sections/providers#24-initialization) says the following (emphasis mine).
> Many feature flag frameworks or SDKs require some initialization before they can be used. They might require **the completion of an HTTP request, establishing persistent connections, or starting timers or worker threads**. The initialization function is an ideal place for such logic.

The types of initialization mentioned above normally require a `context.Context` parameter to be passed. For example, to make an HTTP request, one most definitely should be passing a `context.Context` parameter.

As for Shutdown, a context can be used to manage timeouts or cancellation.

The context is also the mechanism through which OpenTelemetry spans and other request-scoped values are propagated. If there is any chance at all that a provider author might perform I/O in the Init and Shutdown functions, then these functions need to have a context parameter.

The `context` [package documentation](https://pkg.go.dev/context) has more details on what contexts are used for and where they should be used.

I propose that the Init and Shutdown functions linked at the top take a `context.Context` parameter for the reasons outlined above. While this is a breaking change, I think it is acceptable given that both [section 2.4](https://openfeature.dev/specification/sections/providers#24-initialization) and [section 2.5](https://openfeature.dev/specification/sections/providers#25-shutdown) of the specification are currently experimental.

Start with openfeature/provider.go lines 64-67 and openfeature/openfeature.go lines 90-92 to inspect the Init and Shutdown declarations. Read their call sites and run the package tests to identify the affected API surface; done means both StateHandler methods and the top-level Shutdown function accept context.Context consistently.

Written by the indexing model from the issue text.