Fix miscellaneous allow list QA issues

[mohdsayed]

Description

• In the allow list feature, an added allowed domain is stored in chrome.contentSettings for the current browser session. However, this created an issue when the user creates multiple windows while using PSAT, as the content setting gets cleared each time a new chrome window is opened.
• Fix parent domain issue reported by QA
• Update context menu text from "Add Domain to Allow List" to "Allow Domain During Session"

Relevant Technical Choices

• Count number of windows before clearing content to ensure that we do not clear it on new window open.
• Do not clear content settings on install

Testing Instructions

Additional Information:

Screenshot/Screencast

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Checklist

• I have thoroughly tested this code to the best of my abilities.
• I have reviewed the code myself before requesting a review.
• This code is covered by unit tests to verify that it works as intended. (NA)
• The QA of this PR is done by a member of the QA team (to be checked by QA).

Related #376