Standardize Factor*

[Affie]

	FactorCompute	FactorDFG	New fields
✓	id::Union{UUID, Nothing}	id::Union{UUID, Nothing}	REMOVE
✓	label::Symbol	label::Symbol	label::Symbol
✓	tags::Set{Symbol}	tags::Set{Symbol}	tags::Set{Symbol}
✓	_variableOrderSymbols::NTuple{N, Symbol}	_variableOrderSymbols::Vector{Symbol}	variableorder::NTuple{N, Symbol}
✓	timestamp::ZonedDateTime	timestamp::ZonedDateTime	timestamp::TimeDateZone
✓	nstime::Nanosecond	nstime::String	REMOVE
✓	solvable::Base.RefValue{Int}	solvable::Int	solvable::Base.RefValue{Int}
✓	smallData::Dict{Symbol, MetadataTypes}	metadata::String	bloblets::Bloblets
✓	observation::FT	observJSON::String	observation::FT
✓	state::FactorState	state::FactorState	hyper::Recipehyper
✓	state::FactorState	state::FactorState	state::Recipestate
✓			blobentries::Blobentries
✓	FT type parameter	fnctype::String	type::TypeMetadata²
✓		_version::VersionNumber
✓	solvercache::Base.RefValue{<:FactorCache}		solvercache¹

1. solvercache is not serialized and de-serialized lazy.
2. Serialization only fields.

What fields should we consider as a dictionary keyed in the same way as Variable.state?

• Maybe Factor.state as well

[Affie]

These 2 remaining questions will be answered in dfg v0.30.

• state::Recipestate might need a state label to allow multiple solves to run against the graph concurrently.
• Cache finalization, see Cache and Scratch #1138.