[Login, Signup, PasswordReset] Migrate from deprecated Grid

[imnasnainaec]

Part of #3787

Notes for review:

• In most places, replaced <Grid> with <Grid2>, <Stack>, <div>, or nothing, as fit the design need.
• <Stack direction="row"> can be used in place of <Grid2> when we don't want the items in the row to wrap to a second row in a narrow window
• <Card> layout was made more consistent across InvalidLink, Login, Signup, ResetRequest, & PasswordReset
• Do a side-by-side visual comparison between this and master (on QA) to make sure appearance is (roughly) the same or (subjectively) improved on all edited components
• Try each edited component with various window widths > 400px (we don't support narrower than that)
• Click "Forgot password?" on the Login page to test ResetRequest; initiate a password reset and click the link sent to your email to test PasswordReset; change a character in the token within that url to test InvalidLink
• Test with a few different UI languages

---

Screenshots of before'n'after

Signup

Login

Password reset request

Password reset requested

Password reset valid token

Password reset invalid token

---

---

This change is 

[codecov]

Codecov Report

❌ Patch coverage is 45.00000% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.13%. Comparing base (843c541) to head (2756381).
⚠️ Report is 23 commits behind head on master.

Files with missing lines	Patch %	Lines
src/components/InvalidLink/index.tsx	0.00%	4 Missing ⚠️
src/components/Login/Login.tsx	50.00%	3 Missing ⚠️
src/components/PasswordReset/ResetPage.tsx	50.00%	3 Missing ⚠️
src/components/PasswordReset/Request.tsx	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3862      +/-   ##
==========================================
- Coverage   74.17%   74.13%   -0.04%     
==========================================
  Files         288      288              
  Lines       10612    10606       -6     
  Branches     1323     1323              
==========================================
- Hits         7871     7863       -8     
- Misses       2354     2358       +4     
+ Partials      387      385       -2     

Flag	Coverage Δ
backend	85.41% <ø> (ø)
frontend	65.57% <45.00%> (-0.07%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[jasonleenaylor]

src/components/PasswordReset/ResetPage.tsx line 0 at r3 (raw file):
So you removed the Back to login button from this component?

[imnasnainaec]

Reviewable status: 0 of 9 files reviewed, all discussions resolved (waiting on @imnasnainaec)

---

src/components/PasswordReset/ResetPage.tsx line at r3 (raw file):

Previously, jasonleenaylor (Jason Naylor) wrote…

So you removed the Back to login button from this component?

Yes, because I changed it to automatically navigate back to login and just toast the result of the reset.

[jasonleenaylor]

Reviewed 2 of 7 files at r1, 7 of 7 files at r3, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @imnasnainaec)