Add indices info in show(io, ::Field) for fields with non-default indices

[navidcy]

Before this PR:

julia> using Oceananigans

julia> grid = RectilinearGrid(size = (5, 5, 4), extent = (100, 100, 20));

julia> η = Field{Center, Center, Face}(grid, indices = (:, :, size(grid, 3)+1))
5×5×1 Field{Center, Center, Face} on RectilinearGrid on CPU
├── grid: 5×5×4 RectilinearGrid{Float64, Periodic, Periodic, Bounded} on CPU with 3×3×3 halo
├── boundary conditions: FieldBoundaryConditions
│   └── west: Periodic, east: Periodic, south: Periodic, north: Periodic, bottom: Nothing, top: Nothing, immersed: ZeroFlux
└── data: 11×11×1 OffsetArray(::Array{Float64, 3}, -2:8, -2:8, 5:5) with eltype Float64 with indices -2:8×-2:8×5:5
    └── max=0.0, min=0.0, mean=0.0

After this PR:

julia> using Oceananigans

julia> grid = RectilinearGrid(size = (5, 5, 4), extent = (100, 100, 20));

julia> η = Field{Center, Center, Face}(grid, indices = (:, :, size(grid, 3)+1))
5×5×1 Field{Center, Center, Face} on RectilinearGrid on CPU
├── grid: 5×5×4 RectilinearGrid{Float64, Periodic, Periodic, Bounded} on CPU with 3×3×3 halo
├── boundary conditions: FieldBoundaryConditions
│   └── west: Periodic, east: Periodic, south: Periodic, north: Periodic, bottom: Nothing, top: Nothing, immersed: ZeroFlux
├── indices: (:, :, 5:5)
└── data: 11×11×1 OffsetArray(::Array{Float64, 3}, -2:8, -2:8, 5:5) with eltype Float64 with indices -2:8×-2:8×5:5
    └── max=0.0, min=0.0, mean=0.0

[glwagner]

I think we should only show it if the indices are non-default?

[navidcy]

I think we should only show it if the indices are non-default?

agreed; have a look now

[siddharthabishnu]

I think we should only show it if the indices are non-default?

agreed; have a look now

I've reviewed the modifications, and they appear satisfactory. Only the non-default indices are displayed, regardless of whether it's a single index value or a range.