More convenient `IndsNetwork` constructors

Make it easier to construct an IndsNetwork from an underlying graph. This works:

julia> is = IndsNetwork(path_graph(3); site_space=Dictionary(1:3, siteinds("S=1/2", 3)), link_space=2)
IndsNetwork{Int64, Index{Int64}} with 3 vertices:
3-element Vector{Int64}:
 1
 2
 3

and 2 edge(s):
1 => 2
2 => 3

with vertex data:
3-element Dictionary{Int64, Vector{Index{Int64}}}
 1 │ Index{Int64}[(dim=2|id=679|"S=1/2,Site,n=1")]
 2 │ Index{Int64}[(dim=2|id=978|"S=1/2,Site,n=2")]
 3 │ Index{Int64}[(dim=2|id=650|"S=1/2,Site,n=3")]

and edge data:
2-element Dictionary{NamedGraphs.NamedEdge{Int64}, Vector{Index{Int64}}}
 1 => 2 │ Index{Int64}[(dim=2|id=951|"1↔2")]
 2 => 3 │ Index{Int64}[(dim=2|id=103|"2↔3")]

but this currently fails:

julia> is = IndsNetwork(path_graph(3); site_space=siteinds("S=1/2", 3), link_space=2)
ERROR: MethodError: no method matching site_space_map(::Type{Int64}, ::Type{Index{Int64}}, ::NamedGraphs.NamedGraph{Int64}, ::Vector{Index{Int64}})
Closest candidates are:
  site_space_map(::Type, ::Type{<:Index}, ::var"##322", ::AbstractDictionary{<:Any, Vector{<:Index}}) where var"##322" at ~/.julia/packages/SimpleTraits/l1ZsK/src/SimpleTraits.jl:331
  site_space_map(::Type, ::Type{<:Index}, ::var"##323", ::AbstractDictionary{<:Any, <:Index}) where var"##323" at ~/.julia/packages/SimpleTraits/l1ZsK/src/SimpleTraits.jl:331
  site_space_map(::Type, ::Type{<:Index}, ::var"##324", ::AbstractDictionary{<:Any, Vector{Int64}}) where var"##324" at ~/.julia/packages/SimpleTraits/l1ZsK/src/SimpleTraits.jl:331
  ...
Stacktrace:
 [1] IndsNetwork{Int64, Index{Int64}}(g::NamedGraphs.NamedGraph{Int64}, link_space::Int64, site_space::Vector{Index{Int64}})
   @ ITensorNetworks ~/.julia/packages/ITensorNetworks/REB7V/src/indsnetwork.jl:44
 [2] IndsNetwork{Int64, Index{Int64}}(g::SimpleGraph{Int64}, link_space::Int64, site_space::Vector{Index{Int64}})
   @ ITensorNetworks ~/.julia/packages/ITensorNetworks/REB7V/src/indsnetwork.jl:51
 [3] (IndsNetwork{Int64})(::Type{DataGraphs.IsUnderlyingGraph{SimpleGraph{Int64}}}, g::SimpleGraph{Int64}, link_space::Int64, site_space::Vector{Index{Int64}})
   @ ITensorNetworks ~/.julia/packages/ITensorNetworks/REB7V/src/indsnetwork.jl:56
 [4] IndsNetwork
   @ ~/.julia/packages/SimpleTraits/l1ZsK/src/SimpleTraits.jl:331 [inlined]
 [5] (IndsNetwork{Int64})(::Type{DataGraphs.IsUnderlyingGraph{SimpleGraph{Int64}}}, g::SimpleGraph{Int64}; link_space::Int64, site_space::Vector{Index{Int64}})
   @ ITensorNetworks ~/.julia/packages/ITensorNetworks/REB7V/src/indsnetwork.jl:132
 [6] #_#38
   @ ~/.julia/packages/SimpleTraits/l1ZsK/src/SimpleTraits.jl:338 [inlined]
 [7] IndsNetwork(::Type{DataGraphs.IsUnderlyingGraph{SimpleGraph{Int64}}}, g::SimpleGraph{Int64}; kwargs::Base.Pairs{Symbol, Any, Tuple{Symbol, Symbol}, NamedTuple{(:site_space, :link_space), Tuple{Vector{Index{Int64}}, Int64}}})
   @ ITensorNetworks ~/.julia/packages/ITensorNetworks/REB7V/src/indsnetwork.jl:136
 [8] #IndsNetwork#40
   @ ~/.julia/packages/SimpleTraits/l1ZsK/src/SimpleTraits.jl:338 [inlined]
 [9] top-level scope
   @ REPL[33]:1

Also some related issues:

julia> IndsNetwork(path_graph(3), 2, Dictionary(1:3, siteinds("S=1/2", 3)))
ERROR: UndefVarError: links_space not defined
Stacktrace:
 [1] IndsNetwork(::Type{DataGraphs.IsUnderlyingGraph{SimpleGraph{Int64}}}, g::SimpleGraph{Int64}, link_space::Int64, site_space::Dictionary{Int64, Index{Int64}})
   @ ITensorNetworks ~/.julia/packages/ITensorNetworks/REB7V/src/indsnetwork.jl:61
 [2] IndsNetwork(g::SimpleGraph{Int64}, link_space::Int64, site_space::Dictionary{Int64, Index{Int64}})
   @ ITensorNetworks ~/.julia/packages/SimpleTraits/l1ZsK/src/SimpleTraits.jl:331
 [3] top-level scope
   @ REPL[38]:1

julia> IndsNetwork{Int}(path_graph(3), 2, siteinds("S=1/2", 3))
ERROR: MethodError: no method matching site_space_map(::Type{Int64}, ::Type{Index{Int64}}, ::NamedGraphs.NamedGraph{Int64}, ::Vector{Index{Int64}})
Closest candidates are:
  site_space_map(::Type, ::Type{<:Index}, ::var"##322", ::AbstractDictionary{<:Any, Vector{<:Index}}) where var"##322" at ~/.julia/packages/SimpleTraits/l1ZsK/src/SimpleTraits.jl:331
  site_space_map(::Type, ::Type{<:Index}, ::var"##323", ::AbstractDictionary{<:Any, <:Index}) where var"##323" at ~/.julia/packages/SimpleTraits/l1ZsK/src/SimpleTraits.jl:331
  site_space_map(::Type, ::Type{<:Index}, ::var"##324", ::AbstractDictionary{<:Any, Vector{Int64}}) where var"##324" at ~/.julia/packages/SimpleTraits/l1ZsK/src/SimpleTraits.jl:331
  ...
Stacktrace:
 [1] IndsNetwork{Int64, Index{Int64}}(g::NamedGraphs.NamedGraph{Int64}, link_space::Int64, site_space::Vector{Index{Int64}})
   @ ITensorNetworks ~/.julia/packages/ITensorNetworks/REB7V/src/indsnetwork.jl:44
 [2] IndsNetwork{Int64, Index{Int64}}(g::SimpleGraph{Int64}, link_space::Int64, site_space::Vector{Index{Int64}})
   @ ITensorNetworks ~/.julia/packages/ITensorNetworks/REB7V/src/indsnetwork.jl:51
 [3] (IndsNetwork{Int64})(::Type{DataGraphs.IsUnderlyingGraph{SimpleGraph{Int64}}}, g::SimpleGraph{Int64}, link_space::Int64, site_space::Vector{Index{Int64}})
   @ ITensorNetworks ~/.julia/packages/ITensorNetworks/REB7V/src/indsnetwork.jl:56
 [4] (IndsNetwork{Int64})(g::SimpleGraph{Int64}, link_space::Int64, site_space::Vector{Index{Int64}})
   @ ITensorNetworks ~/.julia/packages/SimpleTraits/l1ZsK/src/SimpleTraits.jl:331
 [5] top-level scope
   @ REPL[40]:1

which both should do the same as this one that is working:

julia> IndsNetwork{Int}(path_graph(3), 2, Dictionary(1:3, siteinds("S=1/2", 3)))
IndsNetwork{Int64, Index{Int64}} with 3 vertices:
3-element Vector{Int64}:
 1
 2
 3

and 2 edge(s):
1 => 2
2 => 3

with vertex data:
3-element Dictionary{Int64, Vector{Index{Int64}}}
 1 │ Index{Int64}[(dim=2|id=795|"S=1/2,Site,n=1")]
 2 │ Index{Int64}[(dim=2|id=27|"S=1/2,Site,n=2")]
 3 │ Index{Int64}[(dim=2|id=844|"S=1/2,Site,n=3")]

and edge data:
2-element Dictionary{NamedGraphs.NamedEdge{Int64}, Vector{Index{Int64}}}
 1 => 2 │ Index{Int64}[(dim=2|id=923|"1↔2")]
 2 => 3 │ Index{Int64}[(dim=2|id=789|"2↔3")]

Start by reproducing the constructor examples in the issue, then read src/indsnetwork.jl around the constructors reported at lines 44, 51, 61, 132, and 136. Compare the working dictionary-based form with the failing vector and keyword forms. Done means the shown IndsNetwork construction variants work consistently without the reported MethodError or UndefVarError.