Add metrics for Brave Search entry percentages

[DJAndries]

Add the following daily metrics, with "is default" attribute enabled:

If you used Brave Search in the past day, what percentage of your initial queries originated from typing a query directly into the address bar?
Brave.Search.OmniboxTypedPercent

1. 1-5%
2. 6-20%
3. 21-80%
4. 81-95%
5. 96-100%

If you used Brave Search in the past day, what percentage of your initial queries originated from clicking a Search Suggestion in the address bar dropdown?
Brave.Search.OmniboxSuggestionPercent

1. 1-5%
2. 6-20%
3. 21-80%
4. 81-95%
5. 96-100%

If you used Brave Search in the past day, what percentage of your initial queries originated from the New Tab Page Search Widget?
Brave.Search.NTPSearchPercent

1. 1-5%
2. 6-20%
3. 21-80%
4. 81-95%
5. 96-100%

[DJAndries]

cc @laurentiugruia