clean up argument processing order

[JeffBezanson]

• load juliarc very early, before start_worker or starting processes
• load juliarc in only one place
• handle -L after starting workers, like the help says
• shorten some of the code

see #10692

[jakebolewski]

@tkelman do you know why this causes the Windows tests to consistently fail? I have a follow up quick fix that addresses #10226.

[tkelman]

Yeah, programs that the spawn tests are calling live in Git/bin which gets added to the path by juliarc https://github.com/JuliaLang/julia/blob/master/contrib/windows/juliarc.jl so evidently that isn't happening early enough or at all here?

[JeffBezanson]

Ah, maybe I want

startup               = (opts.startupfile != 2)

instead?

[mbauman]

Loading .juliarc.jl this early means that we can no longer make modifications to the REPL. I simply had using TerminalExtensions in my juliarc (which no longer works), and I'm pretty sure this will also affect folks who were changing their keymaps or things like that.

[KristofferC]

FWIW modifications can still be done with atreplinit but directly changing fields in the repl does not work (because it doesn't exist yet).