Add ability to modify provider options at runtime

[RyanUnderhill]

Now a provider can be chosen and configured purely at runtime, to override what the genai_config.json specifies.
auto config = OgaConfig::Create("path\to\model"); config->SetProviderOption("cuda", "enable_quantum_drive", "1"); auto model = OgaModel::Create(*config);
vs this if no runtime changes are needed (this is also the current API):
auto model = OgaModel::Create("path\to\model");

This will solve the following use cases:

• User wants to change a runtime option for a provider already specified in the genai_config.json
• User wants to switch which provider is used vs what the genai_config.json specifies
• The genai_config.json specifies no provider, and one is completely chosen at runtime.

The OgaConfig provides these methods:

• ClearProviders() - Remove all providers currently specified (will default to cpu if nothing else happens)
• SetProvider("provider_name") - If provider is already exists, does nothing, otherwise adds to end of provider list
• SetProviderOption("provider_name", "option_name", "option_value") - If provider doesn't exist, adds it to end of list. Then sets an option on the provider.

[skyline75489]

This should be `ai_onnxruntime_genai_Config.h"

[RyanUnderhill]

I just noticed that too.