feat(collections): introduce Set, SetInterface, MutableSet, and MutableSetInterface

[azjezz]

introduce the following new types:

• Set
• MutableSet
• SetInterface
• MutableSetInterface

map and mapWithKeys methods have been removed from collection interfaces, they are now present only in Map, MutableMap, MapInterface, MutableMapInterface, Vector, MutableVector, VectorInterface, MutableVectorInterface, Set, MutableSet, SetInterface, and MutableSetInterface. ( the reason is that both map and vector map using the signature map<U>(c: f(V): U) -> Self<K, U> while sets map using map<U>(c: f(V): U) -> Self<U, U> signature ).

[azjezz]

@veewee i need Set/MutableSet in another project, hope the change regarding the other interfaces does not break anything for you :)

[azjezz]

note: this change will be part of v3, but in v4, I plan on removing the current Psl\Collection component, and replacing it with a new implementation that is more rust-ish ( see https://doc.rust-lang.org/std/collections/index.html ) that makes use of Psl\Option and Psl\Result, as the current implementation was initially supposed to be ( a sort of still is )
a PHP port HH\ collections in HHVM ( https://docs.hhvm.com/hack/arrays-and-collections/object-collections )

[coveralls]

Pull Request Test Coverage Report for Build 9762814914

Details

• 208 of 208 (100.0%) changed or added relevant lines in 8 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.07%) to 97.339%

---

Files with Coverage Reduction	New Missed Lines	%
src/Psl/DateTime/Internal/high_resolution_time.php	2	80.95%

Totals
Change from base Build 9562221483:	0.07%
Covered Lines:	5231
Relevant Lines:	5374

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💛 - Coveralls

[joshrai]

Looks good! Just left a few minor comments.

[veewee]

Looks like a good place to start from.
I don't think the changes will break anything from my end, since I'm just using the provided classes instead of interfaces.

Added some comments here and there.

[coveralls]

Pull Request Test Coverage Report for Build 9977328873

Details

• 207 of 217 (95.39%) changed or added relevant lines in 8 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.1%) to 97.158%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/Psl/Type/Internal/MutableSetType.php	38	39	97.44%
src/Psl/Type/Internal/SetType.php	38	39	97.44%
src/Psl/Collection/MutableSet.php	62	66	93.94%
src/Psl/Collection/Set.php	40	44	90.91%

Files with Coverage Reduction	New Missed Lines	%
src/Psl/DateTime/Internal/high_resolution_time.php	2	80.95%

Totals
Change from base Build 9562221483:	-0.1%
Covered Lines:	5230
Relevant Lines:	5383

---

💛 - Coveralls