[Extensions] Get extension loaded params from render process context.

Previously extension loaded parameters to be sent to the renderer
process came from two places:

  * On renderer process initialization: from BrowserContext associated
    with the RenderProcessHost
  * On new extension loaded (e.g. when enabling a new extension for
    incognito/OffTR): from the BrowserContext of the current process

Because the OffTR and OnTR BrowserContexts send their extension to all
running renderer processes this caused spanning mode extension to have
an activation token set for them when they should not have one.

After this change the parameters are only generated from BrowserContext
associated with the RenderProcessHost so the token should only be set if
it needs to be.

A later CL CHECK()s that spanning mode extensions cannot have a token in
an OffTR renderer process. Currently the token was always sent if the
OffTR process is opened before the extension is activated in OffTR.
After this fix the token should never be sent because the correct
BrowserContext is being used.

Bug: 357889496
Change-Id: I1c4ed1fcefd3f7dcbece18ad74109c6d03043cf8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5868610
Reviewed-by: Devlin Cronin <rdevlin.cronin@chromium.org>
Commit-Queue: Justin Lulejian <jlulejian@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1357326}