Tests for `asset/snippets/test/` need to be refactored

[ahrarmonsur]

The language repo migration for googleapis/nodejs-asset created the following PR:
#2856

The PR was blocked due to failing tests, which are all in one filetests/samples.test.js. The advice from @grayside to unblock the migration PR was to:

• keep the tests in the migration
• remove the workflow for the asset samples
• create an issue capturing the follow-on work

The language maintainers are to:

• refactor the tests into individual files corresponding to the sample
• generate the workflow for asset/snippets again

This is captured in this conversation.