Add Extract to function and Extract to private member refactorings

[xperiandri]

Stacked on #20537.

Offers Ctrl+. on a selected expression to move it into a local function, a module function, or, when it uses this or base, a private member. Values the selection reads from the enclosing function become parameters in first-use order.

Parameters are annotated by default because the new function is its own generalization point; the new Parameter types in Extract to function option under Code Fixes can relax that. Not offered when the selection assigns to a captured mutable or reads a byref value.

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✅ Found changes and release notes in following paths:

Change path	Release notes path	Description
`vsintegration/src`	docs/release-notes/.VisualStudio/18.vNext.md

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🔍 Tooling Safety Check — Affects-Design-Time
Affects-Design-Time: Modifies Visual Studio code executed while projects are open.

Generated by PR Tooling Safety Check · gpt56 1.8M · ◷

[T-Gro]

🤖🕵️ Please shorten the description using this guidance. Focus on the problem and why the change is needed, in simplified technical English. Leave the implementation inventory to the Files tab and retain necessary caveats.

[xperiandri]

Covered cases

Offered

• Values the selection uses from the enclosing declaration become parameters of a local function: printfn "%d" (w * h + 1) → let extractedFunction (w: int) (h: int) = w * h + 1 + printfn "%d" (extractedFunction w h)
• The module function is inserted before the declaration that uses it: let private extractedFunction (w: int) (h: int) = w * h + 1 above let area …
• Selecting (w * h + 1) with its parentheses gives the same result, and the call stays parenthesized
• A selection that uses no outside values becomes a function of unit: 1 + 2 → let extractedFunction () = 1 + 2 + extractedFunction ()
• A selection that uses this becomes a private member after the enclosing member: l * this.Rate in List.sumBy (fun l -> l * this.Rate) → this.ExtractedMethod(l) + member private this.ExtractedMethod(l: int) = l * this.Rate
• The parameter-annotation option: Always → let extractedFunction (s: string) (n: int) =, WhenNeeded → (s: string) n (only the receiver of s.ToUpper() is annotated), Never → s n
• Which actions appear: a plain selection (w * h + 1) offers "Extract to local function" and "Extract to module function"; a selection using base (base.ToString() + "!") offers only "Extract to private member"
• A caret in the header of a parenthesized lambda (x -> in (fun x -> x + n)) offers the same actions, with the same results, as selecting the whole (fun x -> x + n)

Not offered

• With no selection, a caret in the lambda body: x + n in (fun x -> x + n)
• The selection assigns to a captured mutable local: for i in 1 .. 3 do n <- n + i
• The selection reads a byref parameter: x + 1 with x: byref<int>