GoogleRefreshTokenProvider should refresh the token if it's expires

[omerlh]

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Is your feature request related to a problem? Please describe.
When having a long running code, the access token will expire and will not be automatically refreshed.

Describe the solution you'd like

withToken method should check if the token expire, and if so, try to refresh it using exchange instead of always returning the token.

Describe alternatives you've considered

I have a working solution that looks like that:

private var compute: Compute {
        get async throws {
            if let tokenProvider = tokenProvider {
                
                let token: Token = try await withCheckedThrowingContinuation{ continuation in
                    do {
                        try tokenProvider.withToken{ token, error in
                            if let token = token {
                                continuation.resume(returning: token)
                            } else if let error = error {
                                continuation.resume(throwing: error)
                            }
                        }
                    } catch{
                        continuation.resume(throwing: error)
                    }
                }
                
                if let creationTime = self.tokenCreationTime, let expiresIn = token.ExpiresIn {
                    let expirationDate = creationTime.advanced(by: Double(expiresIn * 60))
                    
                    print(expirationDate)
                    print(Date().advanced(by: -(5 * 60)))
                    
                    if (expirationDate > Date().advanced(by: -(5 * 60))) {
                        self.tokenProvider = try self.tokenProviderFactory()
                        self.tokenCreationTime = Date()
                    }
                }
                
                return Compute(tokenProvider: tokenProvider)
            } else {
                let tokenProvider = try self.tokenProviderFactory()
                self.tokenProvider = tokenProvider
                self.tokenCreationTime = Date()
                return Compute(tokenProvider: tokenProvider)
            }
        }
    }

But I think this is better suited in the library itself as this is a common problem...