feat: allow configuring OIDC email claim and OIDC auth url parameters (#6867)

This commit:

- Allows configuring the OIDC claim Coder uses for email addresses (by default, this is still email)
- Allows customising the parameters sent to the upstream identity provider when requesting a token. This is still access_type=offline by default.
- Updates documentation related to the above.

cli/testdata/coder_server_--help.golden

@@ -261,6 +261,9 @@ can safely ignore these settings.
       --oidc-allow-signups bool, $CODER_OIDC_ALLOW_SIGNUPS (default: true)
           Whether new users can sign up with OIDC.
 
+      --oidc-auth-url-params struct[map[string]string], $CODER_OIDC_AUTH_URL_PARAMS (default: {"access_type": "offline"})
+          OIDC auth URL parameters to pass to the upstream provider.
+
       --oidc-client-id string, $CODER_OIDC_CLIENT_ID
           Client ID to use for Login with OIDC.
 
@@ -270,6 +273,9 @@ can safely ignore these settings.
       --oidc-email-domain string-array, $CODER_OIDC_EMAIL_DOMAIN
           Email domains that clients logging in with OIDC must match.
 
+      --oidc-email-field string, $CODER_OIDC_EMAIL_FIELD (default: email)
+          OIDC claim field to use as the email.
+
       --oidc-group-field string, $CODER_OIDC_GROUP_FIELD
           Change the OIDC default 'groups' claim field. By default, will be
           'groups' if present in the oidc scopes argument.