Add legacy field in spec

[steveny91]

What does this PR do?

Add a legacy field to deprecated/unmaintained parameters in the spec files.

The checks that have a legacy implementations are:

aerospike
amazon_msk
aspdotnet
cilium
cockroachdb
coredns
dotnetclr
envoy
exchange_server
gitlab
haproxy
hyperv
iis
istio
kong
linkerd
openmetrics
win32_event_log

The checks edited here are some of the ones that don't load a specific legacy template. The other ones I'll have to potentially edit the template to include the legacy field.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.08%. Comparing base (ae03189) to head (72695f3).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

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