Add List.chooseV, Seq.tryPickV, etc. for ValueOption

# Add List.chooseV, Seq.tryPickV, etc. for ValueOption

I propose we add `ValueOption` equivalents of the following functions:

* `List.choose` / `Seq.choose` / `Array.choose` / `Event.choose` / `Observable.choose`
* `List.pick` / `Seq.pick` / `Array.pick` / `Map.pick`
* `List.tryPick` / `Seq.tryPick` / `Array.tryPick` / `Map.tryPick`
* `List.unfold` / `Seq.unfold` / `Array.unfold`

(For the sake of completeness: Additional functions in these modules that could be implemented too are all the `tryX` functions that only *return* an option, but in this suggestion, I choose to concentrate only on the above since they allocate N objects instead of 1).

The existing way of approaching this problem in F# is... none, really, apart from writing low-level implementations similar to what would go into FSharp.Core.

## Pros and Cons

The advantages of making this adjustment to F# are:
* Increased performance, since we can use `choose` and `pick` semantics without N allocations
* Allows later replacing F# internal `Option`-based usages (of `choose` etc.) with `ValueOption`-based (`chooseV` etc.) for likely increased performance
* Better feature parity with `option`

The disadvantages of making this adjustment to F# are:
* Added function bloat (I'd say that for these N-allocating functions it's worth it)

## Extra information

Estimated cost (XS, S, M, L, XL, XXL): S

Related:
* [Previous discussion in dotnet/fsharp](https://github.com/dotnet/fsharp/issues/6467)
* [Implementation PR](https://github.com/dotnet/fsharp/pull/6781)

## Affidavit (please submit!)

Please tick this by placing a cross in the box:
* [x] This is not a question (e.g. like one you might ask on [stackoverflow](http://stackoverflow.com)) and I have searched stackoverflow for discussions of this issue
* [x] I have [searched both open and closed suggestions on this site](http://github.com/fsharp/fslang-suggestions/issues) and believe this is not a duplicate
* [x] This is not something which has obviously "already been decided" in previous versions of F#. If you're questioning a fundamental design decision that has obviously already been taken (e.g. "Make F# untyped") then please don't submit it.

Please tick all that apply:
* [x] This is not a breaking change to the F# language design
* [x] I or my company would be willing to help implement and/or test this

Start with the previous discussion in dotnet/fsharp/issues/6467 and the implementation PR linked in this issue, then compare the requested List, Seq, Array, Event, Observable, and Map functions. Done means reaching agreement on the ValueOption API equivalents and completing the implementation and testing work described by the related PR.

Written by the indexing model from the issue text.