add targeting rule for users with either Google or Bing set as their default search engine

[cbellini]

Targeting rule for users with either Google or Bing set as their default Firefox search engine.

Because

• we are launching a recent searches New Tab page widget experiment (https://docs.google.com/document/d/1e2zXsEYXJuP_OUvB5qwkmAVuhBhyb3n4szWLwT2D5yk/edit) that will only target users that have their default search engine set to one that offers trending search suggestions (which is only Google and Bing currently).

This commit

• adds a targeting rule for users with either Google or Bing set as their default Firefox search engine

[freshstrangemusic]

r+ -- please reformat with either make code_format (requires docker) or pipx run ruff format ./experimenter && pipx run ruff check --fix ./experimenter (if you have pipx installed).

[freshstrangemusic]

You might have to rebase on latest main as well -- there were some issues with some tests failing intermittently becoming a perma fail recently