Moved deprecated Value.get* methods to single-valued types.

[danieldietrich]

Fixes #2450

This is a DRAFT pull request for deprecating the Value methods and moving them to the right locations. The main ideas are described in the blog post Purifying the API surface area.

Renaming things isn't a good idea regarding backward compatibility, however, moving some APIs to the right place is essential for the health of the Vavr library. Here are the main changes I did in this PR:

Removed from Value and sub-classes (without replacement):

• isAsync()
• isSingleValued()
• out(PrintStream), out(PrintWriter)
• stdout(), stderr()
• eq(Object), corresponds(Iterable, BiPredicate) --> Java has its own notion for equality. introducing a new notion, especially across a complex type hierarchy, is questionable
• forEach --> contained in super-interface java.lang.Iterable

Moved from Value to Traversable:

• isLazy()
• map(Function)
• peek(Consumer)
• stringPrefix()
• contains(Object)
• exists(Predicate)
• forAll(Predicate)
• forEach(Consumer)
• collect
• to*(...) conversion functions

Moved from Value to Option, Try, Either, Validation, Future:

• isEmpty
• map(Function) -->
• selected to*(...) conversion functions
• spliterator()

Moved Foldable.* to Traversable and removed Foldable interface:

• Note: its only purpose was to internally structure the code

Removed from collections:

• get*(...) --> they belong to Option, Either, Try, Validation and Future
• reject(predicate) --> use filterNot(predicate) or filter(predicate.negate())
• removeAll(predicate) --> use filter(predicate)

Removed from Either (without replacement):

• left() and Either.LeftProjection --> use swap()
• right() and Either.RightProjection --> Either is right biased

Removed from Future (without replacement):

• DEFAULT_EXECUTOR_SERVICE --> use DEFAULT_EXECUTOR instead
• ofSupplier(...), ofCallable(...), ofRunnable(...) --> use of(...) instead

Removed from Promise (without replacement):

• executorService() --> use the executor() instead

Removed HashCodes interface (without replacement)

Removed from PartialFunction (without replacement):

• removed lift(), unlift() and getIfDefined()

[codecov-io]

Codecov Report

Merging #2557 into master will increase coverage by 0.21%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master    #2557      +/-   ##
============================================
+ Coverage      92.8%   93.02%   +0.21%     
- Complexity     5300     5551     +251     
============================================
  Files            89       89              
  Lines         12706    13101     +395     
  Branches       1609     1660      +51     
============================================
+ Hits          11792    12187     +395     
  Misses          727      727              
  Partials        187      187

Impacted Files	Coverage Δ	Complexity Δ
src/main/java/io/vavr/collection/Traversable.java	96.56% <ø> (ø)	106 <0> (ø)	⬇️
src/main/java/io/vavr/Value.java	93.83% <ø> (ø)	145 <0> (ø)	⬇️
src/main/java/io/vavr/Lazy.java	100% <ø> (ø)	35 <0> (ø)	⬇️
src/main/java/io/vavr/control/Option.java	92.77% <ø> (ø)	46 <0> (ø)	⬇️
src/main/java/io/vavr/control/Try.java	96.54% <100%> (+0.07%)	109 <6> (+6)	⬆️
src/main/java/io/vavr/concurrent/Future.java	97.72% <100%> (+0.07%)	133 <6> (+6)	⬆️
src/main/java/io/vavr/control/Validation.java	96.49% <100%> (+0.11%)	65 <6> (+6)	⬆️
src/main/java/io/vavr/control/Either.java	97.42% <100%> (+0.07%)	65 <6> (+6)	⬆️
src-gen/main/java/io/vavr/Tuple2.java	89% <0%> (+6.18%)	53% <0%> (+22%)	⬆️
src-gen/main/java/io/vavr/Tuple1.java	85.91% <0%> (+8.13%)	37% <0%> (+16%)	⬆️
... and 6 more

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[codecov-commenter]

Codecov Report

Merging #2557 into master will increase coverage by 0.18%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master    #2557      +/-   ##
============================================
+ Coverage     92.84%   93.02%   +0.18%     
- Complexity     5347     5551     +204     
============================================
  Files            89       89              
  Lines         12740    13101     +361     
  Branches       1608     1660      +52     
============================================
+ Hits          11828    12187     +359     
- Misses          723      727       +4     
+ Partials        189      187       -2     

Impacted Files	Coverage Δ	Complexity Δ
src/main/java/io/vavr/Lazy.java	100.00% <ø> (ø)	35.00 <0.00> (ø)
src/main/java/io/vavr/Value.java	93.83% <ø> (ø)	145.00 <0.00> (ø)
src/main/java/io/vavr/collection/Traversable.java	96.56% <ø> (ø)	106.00 <0.00> (ø)
src/main/java/io/vavr/control/Option.java	92.77% <ø> (+1.10%)	46.00 <0.00> (-2.00)	⬆️
src/main/java/io/vavr/concurrent/Future.java	97.72% <100.00%> (+0.07%)	133.00 <6.00> (+6.00)
src/main/java/io/vavr/control/Either.java	97.42% <100.00%> (+0.07%)	65.00 <6.00> (+6.00)
src/main/java/io/vavr/control/Try.java	96.54% <100.00%> (+0.07%)	109.00 <6.00> (+6.00)
src/main/java/io/vavr/control/Validation.java	96.49% <100.00%> (+0.11%)	65.00 <6.00> (+6.00)
src/main/java/io/vavr/collection/Seq.java	90.00% <0.00%> (-6.16%)	40.00% <0.00%> (-6.00%)
src/main/java/io/vavr/collection/Map.java	94.44% <0.00%> (-3.64%)	33.00% <0.00%> (ø%)
... and 37 more

---

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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