Refactor `gr.Blocks.load()` in 4.0

[abidlabs]

gr.Blocks.load() is both a class method and an instance method, which is confusing. We should refactor this in 4.0.

Here's a proposal:

• Deprecate gr.Blocks.load() and gr.Interface.load()
• Instead of the class method, define a gr.load() that can be used to load any Space whether it be Blocks/Interface, or a model
• For the event trigger, define an instance method Blocks.page_load()

[aliabd]

+1 to this, I was confused myself.

[freddyaboulton]

This is already done on v4 but Blocks.load is now an instance method and only defines load events. No page_load was added.