1804236 - Add an optional parameter to `AddKeyLabelFormat` and `AddKeyFormat` and remove their Searchable versions

Status: NEW

(Core :: Gecko Profiler, task, P3)

Description

[Nazım Can Altınova [:canova][:canaltinova on phabricator]]

Currently we have AddKeyLabelFormat and AddKeyFormat for adding a new field to marker schema. But we also have AddKeyLabelFormatSearchable and AddKeyFormatSearchable versions when we need to make them searchable.
These later 2 methods make it harder to change any fields to searchable fields. We can instead change the former main 2 methods to accept an optional Searchable parameter and default it to false. This could make things cleaner.