`integration` pytest mark we use in our test suite is a misnomer

Summary

The integration pytest mark we use in our test suite is a misnomer. In reality, tests with this mark are not necessarily integration tests, we use the mark to label tests which use a sandbox. It would be nice to replace this mark with one which better reflects its use.

Possible fixes

Replace integration pytestmark with sandboxed mark or similar.

Other relevant information

This was originally discussed in the comments on !1158 (merged)

• BuildStream version affected: /milestone %BuildStream_v1.x

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