[web] Use signedIdentityKeysBlobSelector in TraditionalLoginForm
Summary: Now that we have signedIdentityKeysBlobSelector, we can use it in TraditionalLoginForm and SIWELoginForm (next diff) to simplify things.
- Try to log in from web.
- Set breakpoint in loginResponder and make sure signedIdentityKeysBlob comes through and is validated as expected.
- Check the cookies table to see if signed_identity_keys column is populated correctly.
Reviewed By: ashoat
Differential Revision: https://phab.comm.dev/D7047