Update from node 12 to node 16 for `asset`, `dataproc`, `functions`, `game-servers`, `healthcare`, `media`

[pattishin]

Update request Follow up work after https://github.com/GoogleCloudPlatform/nodejs-docs-samples/pull/3464. The following samples are using node 12 and require extra updates are necessary in order to fully support node 16.

• asset/snippets
• dataproc
• functions/imagemagick
• functions/slack
• game-servers/snippets
• healthcare/consent
• healthcare/datasets
• healthcare/dicom
• healthcare/fhir
• healthcare/hl7v2
• media/livestream