[STR-530] Allow platform to set env

[frostbournesb]

Notes:
All the env vars must be present to bundle, copy over .env.example exactly.

apiKey no longer goes into the payload, the iframe does nothing with it so it does not belong in payload, it has been renamed to publicKey since secret keys are in the works, now the user will pass the publicKey to the init function onmount, this puts it more in line with checkout's SDK.

the VITE_ANALYTICS_SUBDOMAIN_URL env var is used now

the services were rearchitected slightly to accommodate

In src/routes/+page.svelte:35

window.StringPay.init({
	env: "LOCAL", // Can be "PROD" | "SANDBOX" | "DEV" | "LOCAL"
	publicKey: apiKey
});

Criteria: All envs (save untestable prod) with their respective api keys work as expected without even needing to rebundle.

[alcalawil]

nice