make workspace() reload .juliarc.jl

[tpapp]

In the manual/FAQ/discussions, workspace() is the recommended way of getting a "clean slate", that should be equivalent to restarting Julia (except for LastMain etc).

Arguably, workspace() then should also reload .juliarc.jl in certain cases.

For example, having an optional reload-startup argument would make sense, with the following options:

1. :auto, which is the default. Reload unless the process was started with --startup-file=no, or -f.
2. false: never reload.
3. true: reload unconditionally.

[tpapp]

In fact, it would be even nicer if there was a more general mechanism to reload code after a call to workspace(). For example, ESS defines a module ESS it uses for interacting with the inferior Julia process, which gets wiped out after workspace().

A solution could be defining a variable workspace-hook, which would be a vector of functions (possibly anonymous) that would be called by workspace(). ESS-like interfaces would just add to this hook (possibly with an API).

[ihnorton]

Related: https://github.com/malmaud/Autoreload.jl

[ihnorton]

crossref #6445

[tomasaschan]

crossref #12314