add highlevel gui + auto legend/colorbar

[SimonDanisch]

This is a proposal for an easy way to add a highlevel GUI and auto legend/colorbar, without any changes to the internal plotting pipeline.
This makes the implementation pretty straightforward and easy to change going forward, at the slight expanse of discoverability & usability.
This works by just wrapping a plot call into GUI(plot(...)), which will then create a GUI like this:

TODOs:

• tests
• more documentation
• precompiles
• finalize API
• what should we do about mutating calls after the call to GUI?

[MakieBot]

Compile Times benchmark

Note, that these numbers may fluctuate on the CI servers, so take them with a grain of salt. All benchmark results are based on the mean time and negative percent mean faster than the base branch. Note, that GLMakie + WGLMakie run on an emulated GPU, so the runtime benchmark is much slower. Results are from running:

using_time = @ctime using Backend
# Compile time
create_time = @ctime fig = scatter(1:4; color=1:4, colormap=:turbo, markersize=20, visible=true)
display_time = @ctime Makie.colorbuffer(display(fig))
# Runtime
create_time = @benchmark fig = scatter(1:4; color=1:4, colormap=:turbo, markersize=20, visible=true)
display_time = @benchmark Makie.colorbuffer(fig)

	using	create	display	create	display
GLMakie	3.68s (3.65, 3.76) 0.05+-	492.74ms (484.70, 497.20) 4.97+-	509.70ms (493.70, 555.47) 20.89+-	7.94ms (7.80, 8.02) 0.09+-	26.34ms (26.25, 26.49) 0.10+-
master	3.76s (3.69, 3.81) 0.04+-	431.59ms (409.06, 460.83) 16.02+-	515.49ms (497.74, 554.02) 20.49+-	7.93ms (7.71, 8.18) 0.19+-	26.37ms (26.26, 26.60) 0.13+-
evaluation	1.02x faster ✓, -0.08s (-1.83d, 0.01p, 0.04std)	0.88x slower❌, 61.15ms (5.16d, 0.00p, 10.49std)	1.01x invariant, -5.79ms (-0.28d, 0.61p, 20.69std)	1.00x invariant, 0.01ms (0.04d, 0.95p, 0.14std)	1.00x invariant, -0.03ms (-0.30d, 0.59p, 0.11std)
CairoMakie	3.13s (3.08, 3.16) 0.02+-	318.01ms (315.62, 324.04) 2.92+-	141.51ms (139.47, 145.15) 1.99+-	7.66ms (7.61, 7.74) 0.05+-	598.94μs (595.77, 600.34) 1.56+-
master	3.08s (3.06, 3.12) 0.02+-	324.32ms (317.07, 343.34) 9.65+-	144.36ms (140.88, 152.61) 4.00+-	7.73ms (7.66, 7.81) 0.06+-	601.96μs (594.92, 609.44) 5.62+-
evaluation	0.98x slower X, 0.05s (2.09d, 0.00p, 0.02std)	1.02x invariant, -6.31ms (-0.88d, 0.14p, 6.29std)	1.02x invariant, -2.85ms (-0.90d, 0.13p, 2.99std)	1.01x faster ✓, -0.07ms (-1.30d, 0.03p, 0.05std)	1.01x invariant, -3.02μs (-0.73d, 0.21p, 3.59std)
WGLMakie	3.89s (3.82, 3.93) 0.04+-	309.45ms (301.23, 314.19) 4.94+-	8.40s (8.35, 8.48) 0.05+-	8.98ms (8.75, 9.10) 0.11+-	69.51ms (66.83, 79.64) 4.64+-
master	3.70s (3.66, 3.74) 0.03+-	318.46ms (306.23, 328.05) 6.55+-	8.48s (8.40, 8.54) 0.05+-	9.00ms (8.81, 9.13) 0.13+-	69.53ms (66.90, 73.54) 2.59+-
evaluation	0.95x slower❌, 0.2s (5.58d, 0.00p, 0.04std)	1.03x faster ✓, -9.01ms (-1.55d, 0.01p, 5.74std)	1.01x faster ✓, -0.08s (-1.65d, 0.01p, 0.05std)	1.00x invariant, -0.02ms (-0.15d, 0.78p, 0.12std)	1.00x invariant, -0.02ms (-0.01d, 0.99p, 3.61std)

[asinghvi17]

Could we also add a method which accepts a figure, so people can "opt-in" to displaying their figures (or maybe even Scenes) in this GUI by default, perhaps by setting a switch in activate!?