RFC: handle colors in Dict limit printing

[KristofferC]

When a dictionary prints values compactly, it cuts off the values after a certain number of characters and writes a couple of dots. In presence of colors, this doesn't work properly, because the computation of the width of the line will be wrong, and the printer might cut off the printing in the middle of the color sequence, corrupting the terminal color state. As an example, the following code

using Random

struct RainBowString
    s::String
end

function Base.show(io::IO, rbs::RainBowString)
    for s in rbs.s
        _, color = rand(Base.text_colors)
        print(io, color, s, "\e[0m")
    end
end


d = Dict([randstring(8) => [RainBowString(randstring(8)) for i in 1:10] for j in 1:5]...)

now shows in the REPL as

with this PR, it shows as:

The original reason for making this PR is that I made some struct print with color but then it printed as:

With this PR, it prints as:

Marking as RFC because I don't know if we want to deal with colors inside containers in the display system outside of MIME("text/plain").
Haven't added tests yet because they are annoying to write and want to see that people are ok with this first.

Fixes #44718

[vtjnash]

I am not sure it is worthwhile to compile this function for every io type it might encounter (which is usually on the order of 5 with various IOContext/TTY/IOBuffer combinations)

Suggested change

	function _truncate_at_width_or_chars(io::IO, str, width, chars="", truncmark="…")
	function _truncate_at_width_or_chars(ignore_ansi::Bool, str, width, chars="", truncmark="…")

[KristofferC]

Good point. Updated.