feat(functors) implement automatic wrapping/unwrapping of optional returns from functor

Needs: Analysis!901 (merged)

This implements:

1. Functors::Optional as alternative to std::optional, please see Functors/Optional.h for motivation.
2. Automatic wrapping and unwrapping by the underlying framework if a chained functor returns a Functors::Optional

ToDo / Questions:

• Not yet implemented is the handling of an optional return value by a functor that is bound to another functor.
• Adapt FunTuple to understand the new optional output cc @amathad

Some smaller fixes for Moore!1461 (closed) :

• add ADDRESSOF functor
• fix RPPVIPCHI2, SHARE_BPV
• enable multiple args for non SIMD input

cc @tfulghes @graven @amathad

mentioned in issue #362 (closed)

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• b11ba8e4 - feat(Functors) implement Functors::Optional, to represent optional functor output
• 7355c6c9 - feat(functors) implement automatic (un)-wrapping when functors return Functors::Optional

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changed title from Draft: fix(functors) for Moore!1461 to Draft: feat(functors) implement automatic wrapping/unwrapping of optional returns from functor

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• 245ed7b7 - feat(functors) implement automatic (un)-wrapping when functors return Functors::Optional

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• 8e62bfe4 - feat(functors) implement automatic (un)-wrapping when functors return Functors::Optional

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• 8e62bfe4...f0118bef - 29 commits from branch master
• 9eb26718 - fix(functors) fix RPPVIPCHI2, SHARE_BPV and enable multiple args for non SIMD input
• 66415b96 - feat(Functors) implement Functors::Optional, to represent optional functor output
• ecd2315d - feat(functors) implement automatic (un)-wrapping when functors return Functors::Optional

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• 0f3b2f6e - feat(functors) implement automatic (un)-wrapping when functors return Functors::Optional

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• 9b0638d9 - feat(functors) implement handling of optional returns of bound functors
• 2ac08be8 - feat(functors) implement test of functors with optional returns

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marked the checklist item Not yet implemented is the handling of an optional return value by a functor that is bound to another functor. as completed

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• 2ac08be8...b9a10d3d - 6 commits from branch master
• fae1edb1 - fix(functors) fix RPPVIPCHI2, SHARE_BPV and enable multiple args for non SIMD input
• 24c82260 - feat(Functors) implement Functors::Optional, to represent optional functor output
• 2176eda0 - feat(functors) implement automatic (un)-wrapping when functors return Functors::Optional
• 9a038821 - feat(functors) implement handling of optional returns of bound functors
• 85d3779f - feat(functors) implement test of functors with optional returns

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• f33e8d19 - fix(functors) introduce Functors::Optional<T>::value_type

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marked the checklist item Adapt FunTuple to understand the new optional output cc @amathad as completed