Push locals of automatic variables to 'DottedScopes' when dotting script cmdlets (#4709)

When dotting a script cmdlet, the locals of automatic variables from the `PSScriptCmdlet` is not set up in the current scope before parameter binding. The fix is to push the locals in `CommandProcessor.OnSetCurrentScope` and pop them in `CommandProcessor.OnRestorePreviousScope`, which will be called from `SetCurrentScopeToExecutionScope` and `RestorePreviousScope` respectively.

Summary of changes:
1. When a new local scope is used, currently we set the locals for `CommandProcessor` right before parameter binding (in `BindCommandLineParametersNoValidation`); we set the locals for `ScriptCommandProcessor` in `Prepare`. I moved both to the constructor, right after the new scope is created so that the code is more consistent.

2. In `CmdletParameterBinderController.cs`, we set up the `PSBoundParameters` and `MyInvocation` variables in `HandleCommandLineDynamicParameters` again, which I think is unnecessary because this method is only called from `BindCommandLineParametersNoValidation`, where the setup is done for the first time.

3. Currently, the locals will be set for dotted script cmdlet in `EnterScope()` and `ExitScope()`. Now, that logic is moved to `OnSetCurrentScope` and `OnRestorePreviousScope` of `CommandProcessor`. This not only makes sure that locals are set before parameter binding, but also is consistent with the `ScriptCommandProcessor`.

test/powershell/engine/ParameterBinding/ParameterBinding.Tests.ps1

@@ -280,4 +280,53 @@
             $_.Exception.Message | should match "Parameter2"
         }
     }
+
+    Context "Use automatic variables as default value for parameters" {
+        BeforeAll {
+            ## Explicit use of 'CmdletBinding' make it a script cmdlet
+            $test1 = @'
+                [CmdletBinding()]
+                param ($Root = $PSScriptRoot)
+                "[$Root]"
+'@
+            ## Use of 'Parameter' implicitly make it a script cmdlet
+            $test2 = @'
+                param (
+                    [Parameter()]
+                    $Root = $PSScriptRoot
+                )
+                "[$Root]"
+'@
+            $tempDir = Join-Path -Path $TestDrive -ChildPath "DefaultValueTest"
+            $test1File = Join-Path -Path $tempDir -ChildPath "test1.ps1"
+            $test2File = Join-Path -Path $tempDir -ChildPath "test2.ps1"
+
+            $expected = "[$tempDir]"
+            $psPath = "$PSHOME\powershell"
+
+            $null = New-Item -Path $tempDir -ItemType Directory -Force
+            Set-Content -Path $test1File -Value $test1 -Force
+            Set-Content -Path $test2File -Value $test2 -Force
+        }
+
+        AfterAll {
+            Remove-Item -Path $tempDir -Recurse -Force -ErrorAction SilentlyContinue
+        }
+
+        It "Test dot-source should evaluate '`$PSScriptRoot' for parameter default value" {
+            $result = . $test1File
+            $result | Should Be $expected
+
+            $result = . $test2File
+            $result | Should Be $expected
+        }
+
+        It "Test 'powershell -File' should evaluate '`$PSScriptRoot' for parameter default value" {
+            $result = & $psPath -NoProfile -File $test1File
+            $result | Should Be $expected
+
+            $result = & $psPath -NoProfile -File $test2File
+            $result | Should Be $expected
+        }
+    }
 }