Add download token and sha to ListRunnerApplicationDownloads

[lupine86]

See #1861

When using Git Hub Enterprise APIs a temp_download_token is included when querying runner downloads via the API.

This PR updates the response structure to include the necessary token and SHA checksum.

>:~$ curl -k -H "Authorization: token $TOKEN" -H "Accept: application/vnd.github.v3+json" https://HOST/api/v3/orgs/actions-sauron/actions/runners/downloads
[
  {
    "os": "osx",
    "architecture": "x64",
    "download_url": "https://HOST/_services/pipelines/_apis/distributedtask/packagedownload/agent/osx-x64/2.277.1",
    "filename": "actions-runner-osx-x64-2.277.1.tar.gz",
    "temp_download_token": "eyJ0eXAiOiJKV1QiLCJhbGciOiJ...",
    "sha256_checksum": "f1fa173889dc9036cd5294..."
  },
  {
    "os": "linux",
    "architecture": "x64",
    "download_url": "https://HOST/_services/pipelines/_apis/distributedtask/packagedownload/agent/linux-x64/2.277.1",
    "filename": "actions-runner-linux-x64-2.277.1.tar.gz",
    "temp_download_token": "eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsIng1...",
    "sha256_checksum": "02d710fc9e0008e641274bb7da7fde61f7c9a..."
  },
  ...
]

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[gmlewis]

To be consistent with the rest of the repo, let's please change this to SHA256Checksum.

[lupine86]

@googlebot I signed it!

[gmlewis]

Thank you, @lupine86 !
Please run go generate ./... and commit/push (not force-push) the changes to this PR.
(More details can be found in CONTRIBUTING.md.)

[codecov]

Codecov Report

Merging #1862 (554c464) into master (576e460) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1862   +/-   ##
=======================================
  Coverage   97.65%   97.65%           
=======================================
  Files         105      105           
  Lines        6769     6769           
=======================================
  Hits         6610     6610           
  Misses         86       86           
  Partials       73       73           

Impacted Files	Coverage Δ
github/actions_runners.go	100.00% <ø> (ø)

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[gmlewis]

Thank you, @lupine86 !
LGTM.
Merging.