[Formatter] Indent Right(hand side) `CommandExpressionAst`

Indent (a multiline) righthand side (list) expression assignment.
Meaning, for a (multiline) Statements.Right CommandExpressionAst (as apposed to Ast's that have already their own embedded indention, as e.g. a PipelineAst), I would like the righthand side to (optionally?) increase the indent:

Wrong way (?)

$List =
'One',
'Two',
'Three'

Correct way

$List =
    'One',
    'Two',
    'Three'

Wrong way (?)

$4 = # or any lengthy variable name aka dot notation
2 + 2

Correct way

$4 = # or any lengthy variable name aka dot notation
    2 + 2

未指定檔案或測試；首先找出 formatter 對 CommandExpressionAst 的處理方式，並與此 issue 中的多行範例進行比較。當多行右側清單或運算式指派獲得所要求的增加縮排，且不變更已自行管理縮排的 AST 結構時，即表示完成。