[tests] [esomx] disable RGB pwm channel(s) when running pwm tests

[scott-brust]

NOTE: This PR should also be backported to 4.x

Problem

wiring/no_fixture_long_running PWM tests are failing on esomx platform, specifically PWM tests with pin C5.
C5 shares a PWM channel with the RGB LEDs (channel 0). When running the PWM long running tests, the RGB led would interfere with the tests, causing them to fail.

Solution

Disabling the RGB LED during the PWM tests allows them to execute without the LED system interfering.

NOTE: this change does affect all PWM tests on all platforms, not just esomx

I tested this PR with esomx, p2 and boron platforms and all passed.

Steps to Test

Run wiring/no_fixture_long_running tests

Example App

Run wiring/no_fixture_long_running tests

References

Links to the Community, Docs, Other Issues, etc..

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Completeness

• User is totes amazing for contributing!
• Contributor has signed CLA (Info here)
• Problem and Solution clearly stated
• Run unit/integration/application tests on device
• Added documentation
• Added to CHANGELOG.md after merging (add links to docs and issues)