IOT RoleAlias support - API and CloudFormation object, enhancements to search_index() response

[jsuchenia]

In this PR I'd like to contribute:

• IoT RoleAlias API: create_role_alias(), list_role_aliases(), describe_role_alias(), update_role_alias(), delete_role_alias()
• AWS::IoT::RoleAlias CloudFormation object

Enhance search() index response - add missing thingGroupNames and shadow fields

[codecov]

Codecov Report

Attention: Patch coverage is 99.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 94.56%. Comparing base (bf49e22) to head (cd0d046).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
moto/iot/models.py	98.71%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #8292   +/-   ##
=======================================
  Coverage   94.56%   94.56%           
=======================================
  Files        1158     1158           
  Lines      100744   100843   +99     
=======================================
+ Hits        95267    95365   +98     
- Misses       5477     5478    +1     

Flag	Coverage Δ
servertests	28.87% <28.00%> (-0.01%)	⬇️
unittests	94.54% <99.00%> (+<0.01%)	⬆️

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[bblommers]

LGTM!

[moto-payments-app]

Hi @jsuchenia,

Thank you so much for contributing to Moto!

To show our thanks, we'd like to share some of the donations that we've received with you. PR's like this are the big reason that Moto is as successful as it is - so it's only fair that you, as a contributor, get to share the spoils.

We've created a companion website with more information:
https://payments.getmoto.org/

Feel free to open a bug or discussion if you run into any problems:
https://github.com/getmoto/payments