[WIP] - PIM v3.0 compatibility

[mmetayer]

TODO:

• [ ] : update composer.json
• [ ] : update indexes for published product and product_proposal (EE); basically that means splitting the index_configuration_ee.yml file in two
• [ ] : Fix/Update the ProductProposalTextCollectionFilter accordingly
• [ ] : fix tests
• [ ] : update README (installation/upgrade)

Breaking changes

ExtendedAttributeTypes::BACKEND_TYPE_TEXT_COLLECTION was renamed from textCollection to text_collection (I couldn't make it work with the former value, probably because of ES version)

[masmrlar]

@mmetayer are there any plans to get this bundle working with version 3.x in the near future?