Check whether a module references itself in 'NestedModules' field in the .psd1 file

This feature ask is per discussion in https://github.com/PowerShell/PowerShell/pull/6843#discussion_r187123774.

Importing a ill-structured module could result in a circular nested module. For example, for the following code, you will see 'True' as the output.

$testdir = Join-Path $env:TEMP test
$testpsm1 = Join-Path $testdir test.psm1
$testpsd1 = Join-Path $testdir test.psd1
mkdir $testdir > $null
Set-Content $testpsm1 -Value "function bar {}"
Set-Content $testpsd1 -Value "@{ ModuleVersion = '0.0.1'; RootModule = 'test'; NestedModules = @('test') }"

$m = Import-Module $testpsd1 -Pass
$m -eq $m.NestedModules[0]
> True

So maybe a rule can be written to check the bold part of test.psd1 "@{ ModuleVersion = '0.0.1'; RootModule = 'test'; NestedModules = @('test') }", to make sure the author is warned when a module like test.psd1 has itself as a nested module.

首先，使用所示的 .psd1 內容重現循環巢狀模組範例，並檢查 PSScriptAnalyzer 如何發現及回報模組問題。當 NestedModules 欄位參照自身的模組產生警告，而有效的巢狀模組宣告不受影響時，這項變更便完成；payload 未指定任何實作檔案或測試。