Move Azure cache implementation to plugin

[ecraig12345]

For the many users of lage (and indirectly backfill) who don't use remote caching, it would be nice if the Azure cache implementation could be moved to a plugin instead of being included by default (due to the significant dependency+parsing bulk). Making this approach extensible would also open the opportunity for other remote cache backends.

Probably something like this:

interface CustomCacheStoragePlugin<TOptions> {
  name: string;
  getProvider: (logger: Logger, cwd: string, options: TOptions) => ICacheStorage;
}

interface CustomCacheStorageConfig<TOptions = unknown> {
  provider: "custom";
  // Can be either a path or a package name.
  // If a package name, it's resolved from the location of the config file.
  // (Maybe come up with a better prop name...?)
  plugin: string;
  options: TOptions;
}

// REMOVED: AzureBlobCacheStorageConfig (now a plugin)
type CacheStorageConfig =
  | { provider: "local" }
  | { provider: "local-skip" }
  | NpmCacheStorageConfig
  | CustomCacheStorageConfig;

// lage.config.js
const lageConfig = {
  cacheOptions: {
    cacheStorageConfig: {
      provider: "custom",
      plugin: "@lage-run/azure-blob-cache-storage",
      options: { /*...*/ }
    }
  }
}