add network audit test for search.brave.com

[diracdeltas]

Description

we should make the network audit test navigate to search.brave.com (or do a search query via NTP widget/omnibox) and make sure no unexpected requests are happening in that process. the search query should be guaranteed to trigger a search ad in order to test that case

Steps to reproduce

n/a

Actual result

n/a

Expected result

n/a

Reproduces how often

Easily reproduced

Brave version (brave://version info)

n/a

Channel information

• [ ] release (stable)
• [ ] beta
• [ ] nightly

Reproducibility

• [ ] with Brave Shields disabled
• [ ] with Brave Rewards disabled
• [ ] in the latest version of Chrome

Miscellaneous information

No response

[diracdeltas]

@vadimstruts (or whoever is taking this) you will probably need to work with the search team to make sure whatever query we use for the test will be guaranteed to trigger an ad