[FEA] Add dropout

[hannahli-nv]

Description

Add the dropout kernel and related tests.

CI Configuration

config:
  build: true
  # valid options are "ops" and "benchmark"
  test: ["ops", "benchmark"]

Checklist

• Code formatted and imports sorted via repo specifications (./format.sh)
• Documentation updated (if needed)
• CI configuration reviewed

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[hannahli-nv]

/ok to test 6c252b6

[xjmxyt]

LGTM, thanks.