Replace compile-time validateFormatting parameter

[scbedd]

Resolves #35153

1. Removes validateFormatting parameter
2. black is opt-out by default, but individual packages can opt in with black = true in their pyproject.toml
3. Update all ci.yml to remove validateFormatting and individually re-enabled black on those packages that were running it prior to this PR.

This change is necessary because of the fact that python - pullrequest doesn't have access to the parameter that you have set for your ci.yml. We need to emplace it some place else that's universal.

I'm taking a look now because @LibbaLawrence ran into exactly this issue with azure-eventhub running on python - pullrequest.

This PR moves these settings from the validateFormatting template parameter to a per-package pyproject.toml.
 
TODO:

• Invert old validate_formatting.py into being called from tox instead of validate_formatting calling `tox.
• update that tox black calling script with is_check_enabled.
• Verify that it still invokes, and doesn't break any dev scenarios (confirm with @kdestin)

[l0lawrence]

Is this going to cause CI failures if an sdk currently has black=True but ValidateFormatting False?

[scbedd]

Is this going to cause CI failures if an sdk currently has black=True but ValidateFormatting False?

Yep.

I'm finding the # of packages that fit in that gap (that aren't mgmt). We don't run black check against mgmt packages. If it's only a few, I'll set pyproject.toml black=False for those packages.

If not...we'll see 😆

[scbedd]

We have one of two avenues:

• We set black check to off by default.
  • I go in and adjust 5 services to update pyproject.toml updates with black=true in them.

OR

• We set black to on by default
  • We omit mgmt packages from checks
  • We individually set black=false on anyone failing (or doesn't currently have validateFormatting: true on their ci.yml)

[l0lawrence]

We have one of two avenues:

* We set `black` check to `off` by default.
  
  * I go in and adjust 5 services to update pyproject.toml updates with `black=true` in them.

OR

* We set `black` to `on` by default
  
  * We omit mgmt packages from checks
  * We individually set `black=false` on anyone failing (or doesn't currently have `validateFormatting: true` on their `ci.yml`)

I think right now black is an opt-in so I would vote for 1 to remain consistent

[scbedd]

I think right now black is an opt-in so I would vote for 1 to remain consistent

Agreed, I'll make that change in this PR after making the other adjustments for opt in.

[azure-sdk]

API change check

API changes are not detected in this pull request.

[scbedd]

/check-enforcer override

Single failure to download an environment seed.