fix(layout): Give Non-numeric flex values priority when media-dependent

[bersLucas]

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• Tests for the changes have been added or this is not a bug fix / enhancement
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PR Type

What kind of change does this PR introduce?

[x] Bugfix [ ] Enhancement [ ] Documentation content changes [ ] Code style update (formatting, local variables) [ ] Refactoring (no functional changes, no api changes) [ ] Build related changes [ ] CI related changes [ ] Infrastructure changes [ ] Other... Please describe: 

What is the current behavior?

Issue Number:
#11466

.layout-column > .flex-##, .layout-row > .flex-## Exists for numeric flex values, but do not for non-numeric flex values, (grow, auto, ect). This means that using a numeric flex value with a non-numeric flex value with a gt/sm/xs prefix will only render the numeric one, even if the media rules should prefer the non-numeric one.

<divlayout="row"><divlayout="column" flex="100" flex-gt-sm="auto"><!-- will always be [flex="100"], even when gt-sm is true --></div></div>

What is the new behavior?

Add more specific rules to the non-numeric mixins,
.layout-row/column > .#{$flexName}-nogrow/initial/auto/noshrink/grow/none.

Does this PR introduce a breaking change?

[ ] Yes [x] No 

Other information

[codymikol]

:partyparrot:

[Splaktar]

As with any changes to layout, we need to evaluate how the change affects the bundle size of the generated CSS.

Can you please post the size numbers of before/after this PR for the angular-material.css and angular-material.min.css files?

I'd love to say that we need some tests for this, however, I realize that our test setup for layouts is somewhere close to inadequate or non-existent. I'll try to do some manual testing on this soon.

[bersLucas]

repository	angular-material.css	angular-material.min.css
angular:master	428kb	322kb
bersLucas:master	448kb (+20kb)	339kb (+17kb)