resourcegroup-append feature is case sensitive

[LucasYao93]

Description

when use resourcegroup-append to get resource group name from resource id. Can not get it if the resource id format as below:

"/subscriptions/xxxxxxxxx/resourcegroups/test-rg/providers/Microsoft.ManagedIdentity/userAssignedIdentities/useids-pwsh-t01"

PS D:\> Get-AzUserAssignedIdentity -ResourceGroupName lucas-rg-test -Name useids-pwsh-t01

Location Name            ResourceGroupName
-------- ----            -----------------
eastus   useids-pwsh-t01

PS D:\> Get-AzUserAssignedIdentity -ResourceGroupName lucas-rg-test -Name useids-pwsh-t01 | fl

ClientId          : xxxxxxxxxxxxxx
Id                : /subscriptions/xxxxxxxxxxxxxxxxxx/resourcegroups/lucas-rg-test/providers/Microsoft.ManagedIdentity/userAssignedIdentities/useids-pwsh-t01
Location          : eastus
Name              : useids-pwsh-t01
PrincipalId       : xxxxxxxxxxxxxxxxxxxx
ResourceGroupName :
Tag               : {
                    }
TenantId          : xxxxxxxxxxxxxxx
Type              : Microsoft.ManagedIdentity/userAssignedIdentities

Autorest version

 Type       Extension Name                           Version      Location
 core       @autorest/core                           3.7.5        C:\Users\v-diya\.autorest\@autorest_core@3.7.5
 extension  @autorest/modelerfour                    4.15.414     C:\Users\v-diya\.autorest\@autorest_modelerfour@4.15.414
 extension  @autorest/powershell                     3.0.472      C:\Users\v-diya\.autorest\@autorest_powershell@3.0.472

[dolauli]

Should have been fixed in #894.