[CI] Add scripts to create a buildkite AMI

[VivekPanyam]

Summary:

This PR enables us to build a buildkite CI stack AMI that has support for GPUs (drivers + container toolkit)

See https://github.com/buildkite/elastic-ci-stack-for-aws for general info on buildkite CI

Test Plan:

• Ran a buildkite pipeline to build an AMI using create_ami.sh and confirmed that the resulting AMI has GPU support
• Confirmed that instances started from that AMI correctly build the rest of Neuropod

[codecov]

Codecov Report

Merging #528 (2766aac) into master (a47d1c8) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #528   +/-   ##
=======================================
  Coverage   87.21%   87.21%           
=======================================
  Files         111      111           
  Lines        7289     7289           
=======================================
  Hits         6357     6357           
  Misses        932      932           

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