Emit `#nowarn` deprecated when something is `Obsolete`

[Booksbaum]

@deprecated is translated into ObsoleteAttribute. When that type (or function or whatever) is used, the compiler emits a warning:

This construct is deprecated. This type is deprecated, please use ...

That's great when writing code. But this is a declaration file -> generated & describes the api to use.

But it's quite common in decl files that something deprecated is referenced in the same decl file somewhere else and that produces a warning:
(source: @types/vscode)

/**
 * @deprecated This type is deprecated, please use [`MarkdownString`](#MarkdownString) instead.
 */
export type MarkedString = MarkdownString | string | { language: string; value: string };
export class Hover {
    contents: MarkedString[];
}

==>

[<Obsolete("This type is deprecated, please use [`MarkdownString`](#MarkdownString) instead.")>]
type MarkedString =
    U4<MarkdownString, string, {| language: string; value: string |}>
type [<AllowNullLiteral>] Hover =
    abstract contents: ResizeArray<MarkedString> with get, set
    //                             ^^^^^^^^^^^^

This construct is deprecated. This type is deprecated, please use MarkdownString instead.

I think in such cases it's reasonable to emit #nowarn "0044" to disable deprecation warnings in that file. (It's only in this file -- if an obsolete type is used somewhere else the F# compiler still warns)

Ideal would be only if there's a usage of something obsolete, but easier probably to always output that nowarn if there's at least one ObsoleteAttribute in the generated file.