Support internal FF default value

[aitorvs]

Task/Issue URL: https://app.asana.com/1/137249556945/project/1202552961248957/task/1210096516271365?focus=true

Description

Add support for "internal" default value in Toggle.DefaultValue.

Steps to test this PR

Code review that all changed values are correct (even if they were changed with find/replace)
Smoke tests the app
Take one feature that is not in remote config:

• change its default value to INTERNAL
• intall play version of the app
• verify feature is not enabled
• install internal version of the app
• verify feature is enabled
• while in internal build, override the remote config (using override config in dev settings) and disable the feature
• verify the feature is disabled
• enable the feature in the remote config
• verify the feature is enabled

[aitorvs]

• Support internal FF default value #5978 👈 (View in Graphite)
• develop

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[CDRussell]

LGTM

• Code reviewed all the changes to ensure they matched their old value still
• Smoke tested
• Took existing kill switch not in remote config, androidSkipUrlConversionOnNewTab, and followed the testing steps. all worked as expected.

Note, there's a merge conflict needing resolved.