web: Sign-up flow alterations for get started page

Created by: philipp-spiess

Fixes #27156 (closed)

This PR changes various /sign-up links in the logged out view of the product to link to the new getting started page where users are educated about our two different deployment models.

️: This PR should only be shipped once the getting started pages are considered ready

Changes in detail

Code pointer	Note
ExtensionRegistry.tsx
OnboardingTour.tsx
ExtensionAreaHeader.tsx	Could not test this locally as extension view is erroring since it's likely missing data
GlobalNavbar.tsx
SearchNotebooksListPage.tsx
ProductSubscriptionForm.tsx	no action
StreamingSearchResults.tsx
ButtonDropdownCta.tsx
SearchContextCtaPrompt.tsx
SignInPage.tsx	no action
CodeMonitoringSignUpLink.tsx