Checker: prevent reporting optional parameter rewritten tree symbols

[auduchinok]

Fixes extra symbols reporting for optional parameters, like in the following:

type T =
    static member M(?a) = ()

The type checker generates an additional attribute, this PR makes its range synthetic, so it doesn't surface as if it was written explicitly.

[github-actions]

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[auduchinok]

The added test assumes #19336 is fixed. There're currently two additional symbols are reported, and the recreated range is not synthetic anymore: