Add the name of build deps to the strict cache key

Description

As it currently stands:

1. When we calculate the weak cache key, we add the names of build dependencies to the cache key: https://gitlab.com/BuildStream/buildstream/blob/master/src/buildstream/element.py#L3095
2. When we calculate the strong cache key, we use the strict cache keys of build deps (and not their names): https://gitlab.com/BuildStream/buildstream/blob/master/src/buildstream/element.py#L3106

This means that changing the name of a dependency would trigger a rebuild with non-strict but not with strict.

Additionally, we store the element_name of build dependencies in the artifact proto: https://gitlab.com/BuildStream/buildstream/blob/master/src/buildstream/_protos/buildstream/v2/artifact.proto#L57

This means that we change the name of a dependency, we not trigger a change in the strict cache key and thus, the proto would get out of sync

This MR addresses this.

added 14 commits

• 78a8566d...cf3f9257 - 12 commits from branch master
• 77eb2556 - tests/frontend/buildcheckout.py: Stop using explicit cache keys
• d9a73dca - element.py: Add the build dependency names to the cache key dict

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mentioned in merge request !1548 (merged)

resolved all threads

approved this merge request

resolved all threads

assigned to @marge-bot123

added 8 commits

• d9a73dca...1f702026 - 6 commits from branch master
• 1461aec9 - tests/frontend/buildcheckout.py: Stop using explicit cache keys
• f296a235 - element.py: Add the build dependency names to the cache key dict

Compare with previous version

assigned to @jennis and unassigned @marge-bot123

I couldn't merge this branch: CI failed!

added 8 commits

• f296a235...dd03a017 - 6 commits from branch master
• 124bb873 - tests/frontend/buildcheckout.py: Stop using explicit cache keys
• 1c560e56 - element.py: Add the build dependency names to the cache key dict

Compare with previous version

approved this merge request

LGTM, though should this take up a NEWS entry about changing cache keys?

approved this merge request

Thanks for the reviews. Closing in favour of !1548 (merged) as this includes identical changes.

closed