Add -DefaultValueType to Should -HaveParameter

[nohwnd]

Fix #1888

Adds -DefaultValueType to both Should -HaveParameter and the assert-style Should-HaveParameter.

The issue wants to tell an expression default apart from a string literal that has the same -DefaultValue text. The catch is that the two are the same type: (Get-DefaultPath) returns a path string and '(Get-DefaultPath)' is a string, so a type alone cannot separate them. The real difference is that one is a computed expression and the other is a literal.

So -DefaultValueType takes a real .NET type, given as a [type] or a type name the same way -Type is given, matched against the type of a literal default. For a computed default whose type is not known until it runs, you pass the special value Expression:

function Connect-Thing {
    param(
        [string] $Url      = (Get-DefaultUrl),    # expression, evaluated at call time
        [string] $Fallback = '(Get-DefaultUrl)',  # literal string that looks identical
        [int]    $Retries  = 3,
        [bool]   $Force    = $false
    )
}

$cmd = Get-Command Connect-Thing
$cmd | Should -HaveParameter Retries -DefaultValueType ([int])       # or -DefaultValueType int
$cmd | Should -HaveParameter Force   -DefaultValueType ([bool])
$cmd | Should -HaveParameter Fallback -DefaultValueType String       # literal string

# The #1888 distinction, same -DefaultValue string, different kind of default:
$cmd | Should -HaveParameter Url      -DefaultValue '(Get-DefaultUrl)' -DefaultValueType Expression
$cmd | Should -HaveParameter Fallback -DefaultValue '(Get-DefaultUrl)' -DefaultValueType String

Notes:

• The type can be a [type] (([bool])) or a type name string (bool, int, string, datetime), same as -Type. An unknown type name throws, and points you at -DefaultValueType Expression.
• Expression covers any computed default whose type is not statically known, e.g. (Get-Date), [datetime]::Now, $someVariable. You cannot assert a concrete type for those, because the type is only known once the code runs.
• $true/$false are [bool], a number is [int]/[double], { ... } is [scriptblock], @{ } is [hashtable]. A $null default has no type. An interpolated string like "$x bar" is [string].
• Failure messages read as, for example, the default value to be of type [System.Int32], but the default value was of type [System.String], or the default value to be an expression, but the default value was of type [System.String].

HaveParameter.ps1 and Should-HaveParameter.ps1 plus tests for both. All existing -HaveParameter behavior is unchanged. test.ps1 for the affected files: 202 passed, no new analyzer findings.

[nohwnd]

doubt that people want to write StringConstantExpressionAst as the expected type of the parameter. need to iterate