Feature/cristian/enable se sc variants

[cmonfortep]

Task/Issue URL: https://app.asana.com/0/414730916066338/1167347031598071/f
Tech Design URL:
CC:

Description:

• Enabling se, sc variants
• Finish LaunchBridgeActivity after being routed to the onboarding.

Steps to test this PR:

SC variant

1. Hardcode variant "sc"
2. Fresh install
3. open the app and navigate to Browser screen
4. perform a search
5. Ensure from the logs that duckduckgo url contains "sc" as part of atb

SC variant

1. Hardcode variant "se"
2. Fresh install
3. open the app and navigate to Browser screen
4. perform a search
5. Ensure from the logs that duckduckgo url contains "se" as part of tab

Finish

1. Fresh install
2. open the app and navigate to Browser
3. click back and ensure no more activities were alive.

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Internal references:

Software Engineering Expectations
Technical Design Template

[malmstein]