refactoring Lazy to take a Supplier()

[lbergelson]

Description

Lazy previously accepted a custom interface called LazyInitializer which is redundant with Supplier since java 8

made LazyInitializer extend Supplier
changed the constructor to take generic Supplier instead of only LazyInitializers

Checklist

• Code compiles correctly
• New tests covering changes and new functionality
• All tests passing
• Extended the README / documentation, if necessary
• Is not backward compatible (breaks binary or source compatibility)

[lbergelson]

@yfarjoun I noticed that we had this pointless class. I deprecated it. It should be backwards compatible with existing code.

[codecov-io]

Current coverage is 63.980% (diff: 91.667%)

Merging #780 into master will increase coverage by 0.148%

@@             master       #780   diff @@
==========================================
  Files           527        527          
  Lines         31733      32124   +391   
  Methods           0          0          
  Messages          0          0          
  Branches       6786       6921   +135   
==========================================
+ Hits          20256      20553   +297   
- Misses         9335       9417    +82   
- Partials       2142       2154    +12   

Diff Coverage	File Path
•••••• 66%	src/main/java/htsjdk/samtools/util/Lazy.java
•••••••••• 100%	src/main/java/htsjdk/samtools/SamInputResource.java
•••••••••• 100%	...sjdk/variant/variantcontext/VariantContextUtils.java

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[yfarjoun]

👍