Implement experimental AWS SageMaker support

[AdeelH]

Overview

Supersedes #1871.

This PR adds the rastervision_aws_sagemaker module which allows running RV jobs on AWS SageMaker in much the same way that rastervision_aws_batch allows running jobs on AWS Batch.

To use this functionality, you can add something like the following to your ~/.ratervision/default configuration file:

[SAGEMAKER]
exec_role=AmazonSageMakerExecutionRole
cpu_image=123.dkr.ecr.us-east-1.amazonaws.com/raster-vision
cpu_instance_type=ml.p3.2xlarge
gpu_image=123.dkr.ecr.us-east-1.amazonaws.com/raster-vision
gpu_instance_type=ml.p3.2xlarge
use_spot_instances=yes

where

• exec_role is an IAM role with appropriate S3 and SageMaker permissions.
• *_image is the URI of a docker image.
• *_instance_type is the instance type. See here for a list.

Checklist

• Added needs-backport label if PR is bug fix that applies to previous minor release
• Ran scripts/format_code and committed any changes
• Documentation updated if needed
• PR has a name that won't get you publicly shamed for vagueness

Notes

• This should be considered very early-stage and experimental.
• It is currently not included in the default pip install rastervision.
• We are not currently making use of SageMaker features like hyperparameter tuning jobs and model deployment.

Testing Instructions

• See new unit tests.
• Run an example with rastervision run sagemaker .. instead of rastervision run batch ...

[codecov]

Codecov Report

Merging #1968 (e22fd18) into master (7106652) will increase coverage by 0.00%.
The diff coverage is 88.88%.

@@           Coverage Diff           @@
##           master    #1968   +/-   ##
=======================================
  Coverage   86.19%   86.20%           
=======================================
  Files         191      193    +2     
  Lines        9362     9434   +72     
=======================================
+ Hits         8070     8133   +63     
- Misses       1292     1301    +9     

Files	Coverage Δ
...s_sagemaker/rastervision/aws_sagemaker/__init__.py	100.00% <100.00%> (ø)
...rastervision/aws_sagemaker/aws_sagemaker_runner.py	87.50% <87.50%> (ø)

... and 1 file with indirect coverage changes