IOT - Improve Job and JobTemplate

[jsuchenia]

Hello

In this PR I'd like to enhance IoT Job object and JobTemplate

[codecov]

Codecov Report

Attention: Patch coverage is 99.05660% with 1 line in your changes missing coverage. Please review.

Project coverage is 94.57%. Comparing base (c8d0e1c) to head (a9da6e4).
Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
moto/iot/models.py	98.73%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #8322   +/-   ##
=======================================
  Coverage   94.57%   94.57%           
=======================================
  Files        1159     1159           
  Lines      100942   101037   +95     
=======================================
+ Hits        95462    95558   +96     
+ Misses       5480     5479    -1     

Flag	Coverage Δ
servertests	28.90% <35.84%> (+<0.01%)	⬆️
unittests	94.54% <99.05%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[bblommers]

LGTM - thank you so much @jsuchenia!