fix(target): Skip fetching proxy server cert

[AprilMay0]

Description

Proxy server certificates are not necessary for or used with CE Targets. As a follow up to #6050 this PR will update LookupTargetForSessionAuthorization to use either a separate function to search for proxy server certificates. In CE this function is empty and returns nil, nil.

The goal of this change is to improve performance by avoiding unnecessary trips to the database for targets that do not have proxy server certificates.

PCI review checklist

• I have documented a clear reason for, and description of, the change I am making.
• If applicable, I've documented a plan to revert these changes if they require more than reverting the pull request.
• If applicable, I've documented the impact of any changes to security controls.
  Examples of changes to security controls include using new access control methods, adding or removing logging pipelines, etc.