Create `NamedDimsArraysNDTensorsExt` and `NamedDimsArraysITensorsExt`

[mtfishman]

Create NamedDimsArraysNDTensorsExt and NamedDimsArraysITensorsExt package extensions for compatibility with NDTensors.jl and ITensors.jl, so that NamedDimsArrays types can be used as backends for ITensor algorithms.

See https://github.com/ITensor/ITensors.jl/tree/v0.7.7/src/lib/ITensorsNamedDimsArraysExt and https://github.com/ITensor/ITensors.jl/tree/v0.7.7/NDTensors/src/NDTensorsNamedDimsArraysExt for references on what should be included.

See also ITensor/ITensors.jl#1601.

[mtfishman]

No longer relevant.