Don't check session storage to determine if a user is logged on

## TODO
- [ ] Edit-ui
- [ ] Create-ui
- [ ] Filings-ui

## What is the problem?
In Edit-UI, Filings-UI and Create-Ui, there are methods like this:

```javascript
/** True if user is authenticated. */
isAuthenticated (): boolean {
const keycloakToken = sessionStorage.getItem(SessionStorageKeys.KeyCloakToken)
// FUTURE: also check that token isn't expired!
return !!keycloakToken
},
```

## What is the impact?
As the code comment warns, the Keycloak token doesn't check that the token is still valid.

## Proposed solution
To determine if a user is authenticated or not, we should check the store of the SbcHeader. In filings-ui, there's a store getter for this purpose, but we have yet to use it.

```javascript
/** Returns true is the user is Keycloak authenticated. */
isKeycloakAuthenticated (state, getters, rootState, rootGetters): boolean {
return rootGetters['auth/isAuthenticated']
}
```