[snapshot] added iPhone 12 models to snapshot reports generator

[nutsmuggler]

Checklist

• I've run bundle exec rspec from the root directory to see all new and existing tests pass
• I've followed the fastlane code style and run bundle exec rubocop -a to ensure the code style is valid
• I've read the Contribution Guidelines
• I've updated the documentation if necessary.

Motivation and Context

The snapshot command generates iPhone 12 screenshot correctly, but the screenshot are not inserted in the screenshots.html file.
After some googling I found out a similar issue, #6690.
This issue, now solved, was related to iPhone SE. After inspecting snapshot/lib/snapshot/reports_generator.rb I realized iPhone 12 models were completely missing.

Description

I added the four models of iPhone 12 to the hash returned by xcode_9_and_above_device_name_mappings.

I then tested the feature by adding the four devices to my app snapfile.
Screenshots were generated correctly.
I also did some tests to make the change worked also with a single device, or a couple.

Testing Steps

Test with a project setup for fast lane snapshots.
Modify your Snapfile to include the four iPhone 12 models, like this:

 devices([
    "iPhone 12",
   "iPhone 12 mini",
    "iPhone 12 Pro",
    "iPhone 12 Pro Max"
 ])

Run bundle exec fastlane snapshot
Verify. the four iPhone 12 models are added to the snapshot.html file.

[google-cla]

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[minuscorp]

LGTM, sign the CLA and it's good to go 🚀

[nutsmuggler]

@googlebot I signed it!

[joshdholtz]

This is great! I actually didn’t know snapshot had this mapping 🤦 I will remember this for the future! Thank you for fixing ❤️

[nutsmuggler]

@joshdholtz thanks! I just thought I'd do it straightaway since it was something simple. Also, an opportunity to learn how to properly do pull request on a public projects. Thank YOU guys for the good work!

[fastlane-bot]

Hey @nutsmuggler 👋

Thank you for your contribution to fastlane and congrats on getting this pull request merged 🎉
The code change now lives in the master branch, however it wasn't released to RubyGems yet.
We usually ship about once a week, and your PR will be included in the next one.

Please let us know if this change requires an immediate release by adding a comment here 👍
We'll notify you once we shipped a new release with your changes 🚀

[fastlane-bot]

Congratulations! 🎉 This was released as part of fastlane 2.181.0 🚀