PSAvoidTrailingWhitespace should ignore empty lines indented to match the current block

Currently, PSAvoidTrailingWhitespace checks all lines for trailing whitespace, even when that line is effectively empty and the "trailing" whitespace is actually leading whitespace for the current indentation level. If the recommended action is taken (remove the whitespace), then adding new code in those spots requires re-indenting that spot to the current code indentation level.

I propose that it should respect the current indentation level for an empty line and not generate a note for those lines, as long as they match the indentation of the current block of code.

What is the latest version of PSScriptAnalyzer at the point of writing
1.17.1, shipping with the vscode-powershell extension version 1.8.1

首先找到 PSAvoidTrailingWhitespace 規則的實作及其現有測試。重現一個縮排至目前區塊層級的空白行案例，然後確認相符的縮排會被忽略，而實際存在的行尾空白仍會被回報。完成的標準是該行為有測試涵蓋，且規則能區分這些情況。