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

[See original issue on GitLab](https://gitlab.com/BuildStream/buildstream/-/issues/949)
In GitLab by [[Gitlab user @phildawson]](https://gitlab.com/phildawson) on Mar 7, 2019, 09:52

## Summary

[//]: # (Summarize the bug encountered concisely)
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

[//]: # (If you can, link to the line of code that might be responsible for the problem)

Replace `integration` pytestmark with `sandboxed` mark or similar.

## Other relevant information

[//]: # (Add the BuildStream version. Substitute below the "x" by "1", "2" or the right version. Add more than one version if necessary)

This was originally discussed in the comments on !1158

* BuildStream version affected: /milestone %BuildStream_v1.x

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Start by searching the test suite for the `integration` pytest mark and review the discussion referenced from !1158. Identify every use that labels sandbox-using tests, then replace the mark consistently with the agreed name. Done means the old mark is no longer used and the test suite still recognizes the replacement.

Written by the indexing model from the issue text.