Move away from keycloak specific library

[olevitt]

We currently use keycloak-js library for authentication.
This library is (as far as I know) specific to keycloak and does not support other providers.
Work on onyxia-api to switch to a provider-agnostic adapter is close to done (see https://github.com/InseeFrLab/onyxia-api/pull/202).
We should do the same for onyxia-web

[garronej]

The job would consist in writing another adapter for this port:
https://github.com/InseeFrLab/onyxia-web/blob/main/src/core/ports/OidcClient.ts

Here is this Keycloak adapter: https://github.com/InseeFrLab/onyxia-web/blob/main/src/core/adapters/keycloakOidcClient.ts Here is the mock adapter: https://github.com/InseeFrLab/onyxia-web/blob/main/src/core/adapters/phonyOidcClient.ts