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

[learn-build-service-prod]

Learn Build status updates of commit d1a13c0:

❌ Validation status: errors

Please follow instructions here which may help to resolve issue.

File	Status	Preview URL	Details
	❌Error		Details

• Line 0, Column 0: [Error: PSMD2Yaml_InternalError] Internal Error: PowerShell script not found: C:\Program Files\docs-pipeline\Scripts\Get-InstalledPlatyPSVersion.ps1

For more details, please refer to the build report.

Note: Your PR may contain errors or warnings or suggestions unrelated to the files you changed. This happens when external dependencies like GitHub alias, Microsoft alias, cross repo links are updated. Please use these instructions to resolve them.

[learn-build-service-prod]

Learn Build status updates of commit d1a13c0:

❌ Validation status: errors

Please follow instructions here which may help to resolve issue.

File	Status	Preview URL	Details
	❌Error		Details

• Line 0, Column 0: [Error: PSMD2Yaml_InternalError] Internal Error: PowerShell script not found: C:\Program Files\docs-pipeline\Scripts\Get-InstalledPlatyPSVersion.ps1

For more details, please refer to the build report.

Note: Your PR may contain errors or warnings or suggestions unrelated to the files you changed. This happens when external dependencies like GitHub alias, Microsoft alias, cross repo links are updated. Please use these instructions to resolve them.