Add the Vercel AI Gateway as a Provider

[fmhall]

We currently have providers for OpenAI, Anthropic, Gemini, and Openrouter.

We'd like to add a provider for the Vercel AI Gateway.

We should accurately capture pricing and use that in our accounting calculations, and add the provider to our SDKs.

This should allow us to then support speech and transcription models, as outlined in the sub-issues below.

[rsproule]

Note that vercel ai has an api get get pricing information

echo/packages/sdk/ts/scripts/update-models.ts

Lines 176 to 179 in 1b6daa1

	export async function fetchGatewayModels(
	gatewayPrefix: string,
	providerName: string
	): Promise<SupportedModel[]> {

which we alr use to update prices elsewhere.

[dhvll]

/attempt #573

[Cyber-Mitch]

Hey @fmhall assign this task to me I want to work on it

[Cyber-Mitch]

/attempt #573