Update alert operation soft button image to display if no soft button capability is present

[joeljfischer]

Fixes #2079

Risk

This PR makes no API changes.

Testing Plan

• I have verified that I have not introduced new warnings in this PR (or explain why below)
• I have run the unit tests with this PR
• I have tested this PR against Core and verified behavior (if applicable, if not applicable, explain why below).

Unit Tests

Added a unit test for when there's no soft button capability

Core Tests

• Alerts with soft button images presented (manticore / Sync).
• Removed soft button capability then presented an alert with a softbutton with an image. Image was presented properly.

Core version / branch / commit hash / module tested against: Manticore (Core 7.1.1), Sync 3.4, Core 8.1.0-develop
HMI name / version / branch / commit hash / module tested against: Manticore (Generic HMI 0.11.0), Sync 3.4, Generic_HMI 0.12.0-develop

Summary

Updated the PresentAlertOperation to send soft button images when the alert soft button image capability is unknown.

Changelog

Bug Fixes

• Alert operation soft button images are now on by default if there's no capability

Tasks Remaining:

• Test against Core with the soft button image capability removed

CLA

• I have signed the CLA