To add Suffix array algorithm implementation (#6530)

* adding Suffix Array Implementation

* adding test for Suffix Array

* patch: lint fix in SuffixArray.java

* patch: lint fix in SuffixArrayTest.java

* fix: private constructor update

* patch: lint fix in suffix array impl

* fix: lint issue line blankspace removal

* fix: checkstype issue

* fix: lint format issue

* Update DIRECTORY.md