Fix V4 compatibility with V3 API

[nzdev]

Builds on #346
Merges V3.x into V4.
Fixed compatibility issues with v3.

[andrewmckaskill]

@nzdev I tried this out today but ran into a breaking conflict.
Examine.Lucene.Directories.DirectoryFactoryBase introduced a new abstract method, CreateTaxonomyDirectory

The existing subclasses won't load anymore and cause an error (for Umbraco it's ConfigurationEnabledDirectoryFactory and LuceneRAMDirectoryFactory):

Could not load all types from "Umbraco.Examine.Lucene, Version=10.6.1.0, Culture=neutral, PublicKeyToken=null" due to LoaderExceptions, skipping:
. System.TypeLoadException on Umbraco.Cms.Infrastructure.Examine.ConfigurationEnabledDirectoryFactory: Method 'CreateTaxonomyDirectory' in type 'Umbraco.Cms.Infrastructure.Examine.ConfigurationEnabledDirectoryFactory' from assembly 'Umbraco.Examine.Lucene, Version=10.6.1.0, Culture=neutral, PublicKeyToken=null' does not have an implementation.
. System.TypeLoadException on Umbraco.Cms.Infrastructure.Examine.LuceneRAMDirectoryFactory: Method 'CreateTaxonomyDirectory' in type 'Umbraco.Cms.Infrastructure.Examine.LuceneRAMDirectoryFactory' from assembly 'Umbraco.Examine.Lucene, Version=10.6.1.0, Culture=neutral, PublicKeyToken=null' does not have an implementation.

[nzdev]

@andrewmckaskill Does that error only appear if the UseTaxonomyIndex option is on? If so, I think implementing a version of ConfigurationEnabledDirectoryFactory which implements the CreateTaxonomyDirectory() method is ok. See how ImageSharp v2/v3 was managed in Umbraco. If not, then we would need to move around the directory sync code as well as the directory code.

[andrewmckaskill]

@nzdev no it appears always. It's because they have directly extended the base class, which now has a new abstract method that has no implementation.

One solution might be to make the method virtual instead of abstract, and to have the default implementation throw a NotImplemetedException.

If the method is only used when Taxonomy is turned on then the default Umbraco implementation won't hit it.

[nzdev]

Done

[Shazwazza]

I think this looks good, will merge