SAML logout: Incorrect log messages

[palakova]

Describe the bug
There are following incorrect log messages, referring to Response instead of Request and vice versa:

OpenSamlLogoutRequestValidator

• "Failed to find issuer in LogoutResponse"
• "Failed to find destination in LogoutResponse"

Saml2LogoutResponseFilter

• "Did not process logout request since failed to find associated RelyingPartyRegistration"

[palakova]

I created PR #12130 to fix this issue. Please feel free to review.