feat: Add IAM GetPolicyOptions support.

[yoshi-automation]

This PR was generated using Autosynth. 🌈

Here's the log from Synthtool:

synthtool > Executing /tmpfs/src/git/autosynth/working_repo/Iot/synth.py.
synthtool > Ensuring dependencies.
synthtool > Pulling artman image.
0.29.1: Pulling from googleapis/artman
Digest: sha256:b2a73f4dda03ef8fcaa973e3ba26d0cf34091f6c22c70add663af325931aef4d
Status: Image is up to date for googleapis/artman:0.29.1
synthtool > Cloning googleapis.
synthtool > Running generator for google/cloud/iot/artman_cloudiot.yaml.
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/php/google-cloud-iot-v1.
synthtool > Replaced 'Copyright \\d{4}' in src/V1/Gapic/DeviceManagerGapicClient.php.
synthtool > Replaced 'Copyright \\d{4}' in tests/Unit/V1/DeviceManagerClientPartialVeneerTest.php.
synthtool > Replaced 'Copyright \\d{4}' in tests/Unit/V1/DeviceManagerClientTest.php.
synthtool > Replaced 'Copyright \\d{4}' in tests/System/V1/DeviceManagerSmokeTest.php.
synthtool > Cleaned up 1 temporary directories.
synthtool > Wrote metadata to synth.metadata.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@59fe42e). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #2130   +/-   ##
=========================================
  Coverage          ?   92.52%           
  Complexity        ?     4430           
=========================================
  Files             ?      305           
  Lines             ?    13157           
  Branches          ?        0           
=========================================
  Hits              ?    12173           
  Misses            ?      984           
  Partials          ?        0

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