Obsolete all -Tags parameters and add alias to -Tag

[maddieclayton]

Description

#3728

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[maddieclayton]

@azuresdkci test this please

[cormacpayne]

@maddieclayton change the parameter name to Tag, add an alias for Tags, update the obsolete message to <cmdlet>: -Tags will be changed to -Tag in an upcoming breaking change release. Please start using the -Tag parameter to avoid breaking scripts., and update the help

[maddieclayton]

on demand run here: https://azuresdkci.westus2.cloudapp.azure.com/view/PowerShell/job/powershell-demand/361/