Improve workspaces inspect truncation

[tompng]

Supports #<ClassName...>, "long_string...", [array...], {key: value...}, (1/12345...), and /long_regexp.../.
If inspect ends with other character, simply use "..." as an omission string.

> pushws "a"*100
> pushws [1]*100
Before: [main, "aaaaaaaaaaaaaaaaaa...>, [1, 1, 1, 1, 1, 1, ...>]
After:  [main, "aaaaaaaaaaaaaaaaaa...", [1, 1, 1, 1, 1, 1, ...]]

Limitation: parens/quotes may not match.

> pushws 1+1ri/2**100
> pushws ["abc"]*10
[main, (1+(1/1267650600228...), ["abc", "abc", "abc...]]

[GabrielLidenor]

I cannot approve it, but it looks great to me.

[GabrielLidenor]

can be simplified a bit, to remove the zero by doing

obj_inspection = "#{obj_inspection[...threshold - 1]}...#{closing}"