feat(Select): Let user personalize icon in Select component

[aljesusg]

Issue #1767

Add feature to Select Component

Let user personalize icon in toggle.
By default is the caret.

[patternfly-build]

PatternFly-React preview: https://1768-pr-patternfly-react-patternfly.surge.sh

[codecov-io]

Codecov Report

Merging #1768 into master will increase coverage by 2.09%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1768      +/-   ##
==========================================
+ Coverage   82.77%   84.87%   +2.09%     
==========================================
  Files         601      355     -246     
  Lines        6642     3788    -2854     
  Branches       72        0      -72     
==========================================
- Hits         5498     3215    -2283     
+ Misses       1117      573     -544     
+ Partials       27        0      -27

Flag	Coverage Δ
#patternfly3	84.87% <ø> (ø)	⬆️
#patternfly4	?
#patternflymisc	?

Impacted Files	Coverage Δ
...4/react-core/src/layouts/Toolbar/ToolbarSection.js
...re/src/components/AboutModal/AboutModalBoxBrand.js
...4/react-charts/src/components/ChartPie/ChartPie.js
...s/patternfly-4/react-tokens/build/templates/esm.js
...t-core/src/components/Modal/ModalBoxCloseButton.js
.../react-core/src/components/Tooltip/TooltipArrow.js
...4/react-core/src/components/Select/SingleSelect.js
...ernfly-4/react-core/src/layouts/Gallery/Gallery.js
...ore/src/components/AboutModal/AboutModalBoxHero.js
...fly-4/react-core/src/components/Card/CardFooter.js
... and 234 more

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[dlabaj]

@kmcfaul Can you take a look at this.

[redallen]

Select is currently being rewritten in TypeScript, so we can address #1767 after it's rewritten.