Use CMake Interface Targets for ZLIB

[blowekamp]

Use "ZLIB:ZLIB" for system zlib libraries from standard CMake find package. For ITK usage of zlib change to use ITK::ITKZLIBModule which include a reference to the selected zlib library.

When the internal ITK library is selected the following export code occurs:

set_target_properties(ITK::ITKZLIBModule PROPERTIES
  INTERFACE_INCLUDE_DIRECTORIES "/scratch/itk/build-release/Modules/ThirdParty/ZLIB/src"
  INTERFACE_LINK_LIBRARIES "ITK::zlib"
)

While when a system zlib is selected:

set_target_properties(ITK::ITKZLIBModule PROPERTIES
  INTERFACE_INCLUDE_DIRECTORIES "/scratch/itk/build-system/Modules/ThirdParty/ZLIB/src"
  INTERFACE_LINK_LIBRARIES "ZLIB::ZLIB"
)

NOTE: Thirdparty ITK modules are still uses the directory property for include directories. I have local changes which can disable this per modules that have not been committed yet.

PR Checklist

• No API changes were made (or the changes have been approved)
• No major design changes were made (or the changes have been approved)
• Added test (or behavior not changed)
• Updated API documentation (or API not changed)
• Added license to new files (if any)
• Added Python wrapping to new files (if any) as described in ITK Software Guide Section 9.5
• Added ITK examples for all new major features (if any)

Refer to the ITK Software Guide for
further development details if necessary.

[dzenanz]

Looks good on a glance.

[blowekamp]

/azp ITK.Windows