Support `From` and `To` static factory methods about mapperly

[latonz]

I'm not sure to what you are referring by if there are no compatible constructors (are you referring to the ones used by CtorMappingBuilder or by NewInstanceObjectMemberMappingBuilder). IMO this new mappings should try to be built directly after CtorMappingBuilder.

IMO the following signatures could be supported (all ordinary, non-async methods returning TTarget):

TSource.ToTTarget()
static TTarget.Create(TSource)
static TTarget.FromTSource(TSource)
static TSource.ToTTarget(TSource)

I'd split them across two MappingBuilders: ConvertInstanceMethodMappingBuilder and ConvertStaticMethodMappingBuilder.

Hints for a contribution despite the contributing documentation:

• Create new entries in Riok.Mapperly.Abstractions.MappingConversionType
• Create new *MappingBuilders, Riok.Mapperly.Descriptors.MappingBuilders.ParseMappingBuilder can be used as an idea how it could work
• Register the new TryBuildMapping methods in Riok.Mapperly.Descriptors.MappingBuilders.MappingBuilder._builders