run "e2e regression tests" in CI once/day, even if they fail all the time

Created by: slimsag

We should be able to run the e2e regression tests described in our release process https://github.com/sourcegraph/sourcegraph/issues/13374 in our CI pipeline:

• Run regression tests:
  • Follow README.md to set up your e2e environment. Run the tests from the web directory. A more complete set of env vars can be found in this 1password entry.
  • New Sourcegraph Docker container:
    • Run the initializer: E2E_INIT=true SOURCEGRAPH_BASE_URL=http://localhost:7080 yarn run test:regression -t 'Initialize new Sourcegraph instance'
    • Run the regression test suite: SOURCEGRAPH_BASE_URL=http://localhost:7080 yarn run test:regression

Actually having these pass is going to not be likely possible in 3.21, but we should aim to have them running (even if they fail all the time) in CI once per day.

https://sourcegraph.com/github.com/sourcegraph/sourcegraph/-/blob/web/src/regression/README.md