Update mlmd and pipelines service to use constructUrl for URL generation

[Gkrumbach07]

https://issues.redhat.com/browse/RHOAIENG-12000

Description

adds a constructUrl option that can be used instead of manually entering service info for backend proxy helper
uses this for mlmd and pipelines

How Has This Been Tested?

make sure a pipelines server and mlmd server can fetch data
create a new pipeline server and verify backend is not crashing

Test Impact

none backend

Request review criteria:

Self checklist (all need to be checked):

• The developer has manually tested the changes and verified that the changes work
• Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has added tests or explained why testing cannot be added (unit or cypress tests for related changes)

If you have UI changes:

• Included any necessary screenshots or gifs if it was a UI change.
• Included tags to the UX team if it was a UI/UX change.

After the PR is posted & before it merges:

• The developer has tested their solution on a cluster by using the image produced by the PR to main

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.27%. Comparing base (05845d6) to head (e90aa58).
Report is 23 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3177   +/-   ##
=======================================
  Coverage   85.27%   85.27%           
=======================================
  Files        1258     1258           
  Lines       27689    27689           
  Branches     7370     7370           
=======================================
  Hits        23613    23613           
  Misses       4076     4076           

see 2 files with indirect coverage changes

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[jpuzz0]

Verified here by creating a pipeline server and verifying mlmd resources were fetched after creating a new run with scalar metrics.

[Gkrumbach07]

/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Gkrumbach07, jpuzz0

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