chore: eliminate need for hasStyles configuration option

[techfg]

Currently, to ensure that custom CSS is packed in a bundle, the hasStyles configuration must be set to true in the bundle.yaml. This has two shortcomings:

1. It's not documented anywhere
2. There should be ways to determine if a runtime.css is present dynamically and include rather than requiring the config option.

I believe rumtime.css should only be present after build if custom css is imported in which case its intended to be used. Assuming that is the case, the option/flag should be able to be removed. At minimum, the config option should be documented.