HelixBootstrapTool: add prompt before remove

[justinlin-linkedin]

Summary

Prompt user to confirm the delete before actually deleting the instance or resource.

[codecov-commenter]

Codecov Report

Attention: 20 lines in your changes are missing coverage. Please review.

Comparison is base (15e7dfa) 72.24% compared to head (c101716) 72.19%.
Report is 2 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2608      +/-   ##
============================================
- Coverage     72.24%   72.19%   -0.06%     
- Complexity    11407    11410       +3     
============================================
  Files           805      806       +1     
  Lines         65097    65139      +42     
  Branches       7936     7945       +9     
============================================
- Hits          47030    47027       -3     
- Misses        15484    15521      +37     
- Partials       2583     2591       +8     

Files	Coverage Δ
...ub/ambry/clustermap/HelixBootstrapUpgradeTool.java	0.00% <0.00%> (ø)
...ub/ambry/clustermap/HelixBootstrapUpgradeUtil.java	72.40% <24.00%> (-0.77%)	⬇️

... and 24 files with indirect coverage changes

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