Fix for Strategies.yaml to include parent_is_proxy and fix some tech debt

[cybertunnel]

Closes: #7638

This PR is to fix an issue where as in #7638, the strategies.yaml does not include a parent_is_proxy value for any servers in the file. This PR also fixes an issue from tech debt where the strategiesdotconfig.go is supposed to be strategiesdotyaml.go since the file changed from .config to .yaml

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Which Traffic Control components are affected by this PR?

• Traffic Control Cache Config (t3c, formerly ORT)

What is the best way to verify this PR?

I have added a test in strategiesdotyaml_tests.go, the function is TestMakeStrategiesDotYAMLParentIsProxy which tests when opt.ParentIsProxy is set to true and when it is set to false.

If this is a bugfix, which Traffic Control versions contained the bug?

I would imagine all existing versions have this issue since switching to .yaml structure.

PR submission checklist

• This PR has tests
• This PR has documentation
• This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY (see the Apache Software Foundation's security guidelines for details)

This PR doesn't need documentation since it has everything already documented in ATS's page. This is just fixing a behavior we were expecting.

[codecov]

Codecov Report

Merging #7639 (6ea8511) into master (08d037f) will increase coverage by 7.24%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #7639      +/-   ##
============================================
+ Coverage     30.12%   37.37%   +7.24%     
  Complexity       98       98              
============================================
  Files           794      250     -544     
  Lines         84077    12676   -71401     
  Branches        907       90     -817     
============================================
- Hits          25332     4738   -20594     
+ Misses        56615     7620   -48995     
+ Partials       2130      318    -1812     

Flag	Coverage Δ
golib_unit	?
grove_unit	4.60% <ø> (ø)
t3c_unit	?
traffic_monitor_unit	?
traffic_ops_unit	?
traffic_portal_v2	?
traffic_stats_unit	10.14% <ø> (ø)
unit_tests	6.00% <ø> (-21.26%)	⬇️

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see 546 files with indirect coverage changes

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