Migrate docs build to use PSMD2Yaml and new page template

[Saisang]

When MAML2Yaml is not in the path of monikerMapping.json, reference content in the docset will be built by PSMD2Yaml instead of its predecessor MAML2Yaml. For details, see https://dev.azure.com/ceapex/Engineering/_workitems/edit/783982

[Saisang]

@sdwheeler Could you fix the errors?

1. "yaml-syntax-error" type error? That's because the metadata has extra "{{}}".
2. azps-12.5.0/Az.CognitiveServices/New-AzCognitiveServicesAccountDeployment.md, Missing required attribute: 'parameters.cmdletParameters.parameterSets.position'.

And the warnings:

1. xref-not-found, File name issue.
2. PSMD2Yaml_InconsistentCmdletsInModule, "Inconsistent cmdlets found in module: Az.Network. 2 cmdlets in the module folder but not listed in the module file: New-AzApplicationGatewayFirewallPolicyException, New-AzPacketCaptureSettingsConfig."

The other errors/warnings would be fixed in next batch by xmdanni.

CC @xmdanni @mtrilbybassett

[sdwheeler]

See fixes in #3670

[Saisang]

@sdwheeler Hi Sean, there is one warning left, would you please refer to this build log and fix it? That's caused by file name case.

CC @mikefrobbins

[sdwheeler]

@sdwheeler Hi Sean, there is one warning left, would you please refer to this build log and fix it? That's caused by file name case.

CC @mikefrobbins

This should be fixed by #3679

[learn-build-service-prod]

Learn Build status updates of commit f580079:

✅ Validation status: passed

File	Status	Preview URL	Details
.openpublishing.publish.config.json	✅Succeeded
mapping/MAML2Yaml/monikerMapping.json	✅Succeeded	n/a (file deleted or renamed)
mapping/monikerMapping.json	✅Succeeded

For more details, please refer to the build report.

[Saisang]

@mtrilbybassett @sdwheeler @xmdanni The PR is ready for review. Preview page https://review.learn.microsoft.com/en-us/powershell/module/az.accounts/add-azenvironment?view=azps-12.5.0&branch=pr-en-us-3667