fix(content): Set email for force_auth with React signin

[vpomerleau]

Because

• If the user reaches a page where they must reauth, for example when following a link from email, we want to suggest the provided email for signin instead of asking the user to re-enter their email (matching parity with backbone)

This pull request

• When reauth is required and there is a redirect to force_auth, set the email on the user model so it can be picked up when navigating to react

Issue that this pull request solves

Closes: #FXA-9855

Checklist

Put an x in the boxes that apply

• [x] My commit is GPG signed.
• [ ] If applicable, I have modified or added tests which pass locally.
• [ ] I have added necessary documentation (if appropriate).
• [ ] I have verified that my changes render correctly in RTL (if appropriate).

Screenshots (Optional)

Please attach the screenshots of the changes made in case of change in user interface.

Other information (Optional)

One way to test:

1. Have an account created with a product subscription (subscribe to a product via 123Done)
2. Sign out of the account
3. From the subscription welcome email, look for the "Update billing information" link a. For backbone: follow the link and observe that redirected to force_auth page to enter password b. For react, without this PR: paste the link into the search bar and add react params forceExperiment=generalizedReactApp&forceExperimentGroup=react. Observe that redirected to index page to re-enter email. c. For react, with this PR: paste the link into the search bar and add react params forceExperiment=generalizedReactApp&forceExperimentGroup=react. Observe that redirected to signin page to enter password (skip index).