feat: add traffic manager backend controller to handle delete

[zhiying-lin]

What type of PR is this?

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

Requirements:

• run make reviewable for basic local test
• Read and followed fleet-networking's Code of conduct.
• uses conventional commit messages
• includes documentation
• adds unit tests

How has this code been tested

Special notes for your reviewer

[codecov]

Codecov Report

Attention: Patch coverage is 45.65217% with 100 lines in your changes missing coverage. Please review.

Project coverage is 77.65%. Comparing base (db04dcd) to head (c9ae512).

Files with missing lines	Patch %	Lines
...ontrollers/hub/trafficmanagerbackend/controller.go	44.94%	83 Missing and 15 partials ⚠️
...ontrollers/hub/trafficmanagerprofile/controller.go	66.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #203      +/-   ##
==========================================
- Coverage   79.66%   77.65%   -2.01%     
==========================================
  Files          26       27       +1     
  Lines        2493     3424     +931     
==========================================
+ Hits         1986     2659     +673     
- Misses        370      613     +243     
- Partials      137      152      +15     

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