Allow the s3 upload task to set metadata (x-amz-meta-) values

[jlamhp]

Is your feature request related to a problem? Please describe.

The current s3 upload task does not allow the ability to set x-amz-meta values. Currently we would be forced to use the cli to do this.

Describe the solution you'd like

An additional optional parameter that takes in an array or map of meta values to set for the object(s) being uploaded Example:

- task: AmazonWebServices.aws-vsts-tools.S3Upload.S3Upload@1
  inputs:
    ....
    metadata:
    - version: "1.2.3.4"
    - customname: customvalue
 

Above command should result in the s3 objects with x-amz-meta-version set to 1.2.3.4 and x-amz-meta-customname to customvalue

Note: I don't know how the above should be property formatted or if there's a better way to do this, however it should operate like the --metadata option in the cli.

Describe alternatives you've considered

We can use the cli to do this, but would prefer to be able to use to the packaged task to make the code more simple.