Consolidate FactorDFG with FactorCompute, and rebuild Factor serialization.

[Affie]

Towards #1179

[github-actions]

Remaining comments which cannot be posted as a review comment to avoid GitHub Rate Limit

JuliaFormatter

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[JuliaFormatter] _{reported by reviewdog 🐶}

DistributedFactorGraphs.jl/src/services/DFGFactor.jl

Line 142 in 4c5d3a8

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[JuliaFormatter] _{reported by reviewdog 🐶}

DistributedFactorGraphs.jl/src/services/DFGVariable.jl

Lines 394 to 395 in 4c5d3a8

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[JuliaFormatter] _{reported by reviewdog 🐶}

DistributedFactorGraphs.jl/test/interfaceTests.jl

Lines 68 to 69 in 4c5d3a8

	"VariableCompute{TestVariableType1, Vector{Float64}, 1}\nid:\nnothing\nlabel:\n:a\ntags:\nSet([:VARIABLE, :POSE])\nsmallData:\nDict{Symbol, Union{Bool, Float64, Int64, Vector{Bool}, Vector{Float64}, Vector{Int64}, Vector{String}, String}}()\ndataDict:\nDict{Symbol, Blobentry}()\nsolvable:\nRefValue{Int64}(0)\n"
	# "VariableCompute{TestVariableType1, Vector{Float64}, 1}\nid:\nnothing\nlabel:\n:a\ntags:\nSet([:VARIABLE, :POSE])\nsmallData:\nDict{Symbol, Union{Bool, Float64, Int64, Vector{Bool}, Vector{Float64}, Vector{Int64}, Vector{String}, String}}(:small=>\"data\")\ndataDict:\nDict{Symbol, Blobentry}()\nsolvable:\n0\n"

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[JuliaFormatter] _{reported by reviewdog 🐶}

DistributedFactorGraphs.jl/test/testBlocks.jl

Lines 1462 to 1463 in 4c5d3a8

	@test fact.variableorder ==
	getFactor(dfg, fact.label).variableorder