Raise error for showSelected2 aesthetic/parameter usage

[biplab-sutradhar]

closes #213
Adds a check for use of showSelected2 (and similar) in aesthetics or parameters, and raises an error matching the unit test:
"Use of clickSelects and showSelected as aesthetics has been deprecated. Please use as parameters."

Prevents silent user errors from typos like showSelected2.

[biplab-sutradhar]

@tdhock there are multiple files such as
Climate-selected.R
test-compiler-plot-named-timexxx.R
test-compiler-save-separate-chunks.R
test-renderer1-geom-label-aligned.R
test-renderer1-WorldBank-NA.R

where showSelected2,showSelected1 is used. I think it would be better to update.

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 3 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (master@d386bd2). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
R/z_animintHelpers.R	66.66%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #215   +/-   ##
=========================================
  Coverage          ?   77.66%           
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  Files             ?      164           
  Lines             ?     8737           
  Branches          ?      542           
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  Hits              ?     6786           
  Misses            ?     1951           
  Partials          ?        0           

Flag	Coverage Δ
javascript	95.33% <ø> (?)
r	69.68% <66.66%> (?)

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[biplab-sutradhar]

when showSelected is a vector, it generates numbered columns (showSelected1, showSelected2) hence if I change other test file it gives error

[biplab-sutradhar]

@tdhock can you please check