hats: Add support for incognito surveys on desktop

This patch adds support for showing surveys in incognito, specifically:

1. HatsService is made available in incognito by using the kOwnInstance
   profile selection and taking into account that we might be using an
   OTR profile. Specifically, it will use the original profile for
   checking the age and reading/writing prefs.

2. RequestedBrowserType is added as an enum that configures the
   requested browser type of the survey, i.e. whether it should be
   shown in regular browsing or incognito. The default is kRegular.

3. Regular browsing check when showing the survey is extended to
   verify other browser types too.

4. RequestedBrowserType is added as a survey config parameter.
   Adding it there makes sure that the choice of survey's requested
   browser type is intentional.

It also adds a check for Android that prevents adding kIncognito
surveys, as there's no support for them on Android.

Bug: 397440273
Change-Id: I3b12da72396770b67e3904af6af81f5558075b38
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6425020
Reviewed-by: Rubin Deliallisi <rubindl@chromium.org>
Commit-Queue: Kamil Jarosz <kjarosz@google.com>
Reviewed-by: Florian Jacky <fjacky@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1447064}