Add rocMLIR kv-cache attention support

[turneram]

[causten]

Note, this PR will need to be "squash and merged" once approved

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 92.41%. Comparing base (695506a) to head (a7f8f96).

Additional details and impacted files

@@                  Coverage Diff                  @@
##           release/rocm-rel-6.4    #3921   +/-   ##
=====================================================
  Coverage                 92.41%   92.41%           
=====================================================
  Files                       520      521    +1     
  Lines                     22472    22474    +2     
=====================================================
+ Hits                      20767    20769    +2     
  Misses                     1705     1705           

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