Change the context menu and Copilot settings icon (#14501)

Felt the link we were using for menu items that open a browser page was
not the best. That one is most typically used for attachments within
scope, as opposed to opening external links. Noticed that via the
"Copilot Settings" menu, which also felt like it could have a bit more
descriptive label. Also reduced the size of the rendered icon in this
component.

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Release Notes:

- N/A