Advanced AssetServer load variants are now exposed through a builder pattern.

In previous versions of Bevy, there were many different ways to load an asset:

• AssetServer::load
• AssetServer::load_acquire
• AssetServer::load_untyped
• AssetServer::load_acquire_override_with_settings
• etc.

All these variants have been simplified to only two variants:

1. AssetServer::load(): This is a convenience method and just calls the load builder internally.
2. AssetServer::load_builder(): allows for constructing more complex loads like untyped loads, loads including guards, loads with settings, etc.

Every load variant above can be reimplemented using load_builder, and each one of these methods has deprecation messages on them explaining their new equivalent. For example, load_with_settings_override can now be replaced with:

asset_server
    .load_builder()
    .with_settings(settings)
    .override_unapproved()
    .load(path)

NestedLoader

To match this change, NestedLoader has been replaced with NestedLoadBuilder. Similarly, LoadContext::loader has been replaced with LoadContext::load_builder. The various calls have now been simplified:

• context.loader().load(path) -> context.load_builder().load(path)
• context.loader().with_dynamic_type(type_id).load(path) -> context.load_builder().load_erased(type_id, path)
• context.loader().with_unknown_type().load(path) -> context.load_builder().load_untyped(path)
• context.loader().immediate().load(path) -> context.load_builder().load_value(path)
• context.loader().immediate().with_dynamic_type(type_id).load(path) -> context.load_builder().load_erased_value(type_id, path)
• context.loader().immediate().with_unknown_type().load(path) -> context.load_builder().load_untyped_value(path)
• context.loader().immediate().with_reader(reader).load(path) -> context.load_builder().load_value_from_reader(path, reader)
• context.loader().immediate().with_reader(reader).with_dynamic_type(type_id).load(path) -> context.load_builder().load_erased_value_from_reader(type_id, path, reader)
• context.loader().immediate().with_reader(reader).with_unknown_type().load(path) -> context.load_builder().load_untyped_value_from_reader(path, reader)