[feat] Emit job options to aprun command line

[vkarak]

Fixes #1017.

[codecov-io]

Codecov Report

Merging #1067 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #1067      +/-   ##
=========================================
+ Coverage   91.69%   91.7%   +<.01%     
=========================================
  Files          81      81              
  Lines       11103   11110       +7     
=========================================
+ Hits        10181   10188       +7     
  Misses        922     922

Impacted Files	Coverage Δ
reframe/core/launchers/mpi.py	98.59% <100%> (+0.15%)	⬆️
unittests/test_launchers.py	93.51% <100%> (ø)	⬆️

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[vkarak]

@jgphpc Can you test that on Tiger?

[vkarak]

As suggested by @TheOneTrueScud, I should change the name of the launcher backend to aprun so as to match documentation + it feels more natural.

[victorusu]

lgtm

[vkarak]

I will eventually not change the name of the scheduler. The documentation is correct. The aprun vs. alps was just an error in our private communications.