Cached failed action is used when retrying a failed build

When using remote execution, if a build fails the failure is saved in the action cache. However builds can fail for a variety of reasons (e.g. running out of resources) that are not necessarily reproducible.

Buildstream offers to retry at the command line and also offers the `--retry-failed` command line argument for this purpose. However, it will still get a cached failure from the action cache.

Here is an example log (I extracted just the things relevant to the element in question):
```
[11:08:35][--:--:--][8524a2f2][ pull:freedesktop-sdk.bst:components/fontconfig.bst] START freedesktop-sdk/components-fontconfig/8524a2f2-pull.20250611-110835.log
[11:08:35][--:--:--][8524a2f2][ pull:freedesktop-sdk.bst:components/fontconfig.bst] STATUS Pulling artifact 8524a2f2 <- https://gbm.gnome.org:11004
[11:08:35][--:--:--][8524a2f2][ pull:freedesktop-sdk.bst:components/fontconfig.bst] STATUS Pulling data for artifact 8524a2f2 <- https://gbm.gnome.org:11004
[11:08:35][--:--:--][8524a2f2][ pull:freedesktop-sdk.bst:components/fontconfig.bst] INFO Pulled artifact 8524a2f2 <- https://gbm.gnome.org:11004
[11:08:35][--:--:--][8524a2f2][ pull:freedesktop-sdk.bst:components/fontconfig.bst] INFO Discarded failed build
[11:08:35][00:00:00][8524a2f2][ pull:freedesktop-sdk.bst:components/fontconfig.bst] SKIPPED Pull
[11:08:35][--:--:--][8524a2f2][ fetch:freedesktop-sdk.bst:components/fontconfig.bst] START freedesktop-sdk/components-fontconfig/8524a2f2-fetch.20250611-110835.log
[11:08:35][--:--:--][8524a2f2][ fetch:freedesktop-sdk.bst:components/fontconfig.bst] STATUS Pulling source 031032b8 <- https://gbm.gnome.org:11004
[11:08:36][--:--:--][8524a2f2][ fetch:freedesktop-sdk.bst:components/fontconfig.bst] STATUS Pulling data for source 031032b8 <- https://gbm.gnome.org:11004
[11:08:36][--:--:--][8524a2f2][ fetch:freedesktop-sdk.bst:components/fontconfig.bst] INFO Pulled source 031032b8 <- https://gbm.gnome.org:11004
[11:08:36][00:00:00][8524a2f2][ fetch:freedesktop-sdk.bst:components/fontconfig.bst] SUCCESS freedesktop-sdk/components-fontconfig/8524a2f2-fetch.20250611-110835.log
[11:08:37][--:--:--][8524a2f2][ build:freedesktop-sdk.bst:components/fontconfig.bst] START freedesktop-sdk/components-fontconfig/8524a2f2-build.20250611-110837.log
[11:08:37][--:--:--][8524a2f2][ build:freedesktop-sdk.bst:components/fontconfig.bst] START Staging dependencies at: /
[11:09:04][00:00:26][8524a2f2][ build:freedesktop-sdk.bst:components/fontconfig.bst] SUCCESS Staging dependencies at: /
[11:09:04][--:--:--][8524a2f2][ build:freedesktop-sdk.bst:components/fontconfig.bst] START Integrating sandbox
[11:09:32][--:--:--][8524a2f2][ build:freedesktop-sdk.bst:components/fontconfig.bst] INFO Action result found in action cache
[11:09:48][00:00:44][8524a2f2][ build:freedesktop-sdk.bst:components/fontconfig.bst] SUCCESS Integrating sandbox
[11:09:48][--:--:--][8524a2f2][ build:freedesktop-sdk.bst:components/fontconfig.bst] START Staging sources
[11:09:48][00:00:00][8524a2f2][ build:freedesktop-sdk.bst:components/fontconfig.bst] SUCCESS Staging sources
[11:09:48][--:--:--][8524a2f2][ build:freedesktop-sdk.bst:components/fontconfig.bst] START Running commands
[11:09:48][--:--:--][8524a2f2][ build:freedesktop-sdk.bst:components/fontconfig.bst] INFO Action result found in action cache
[11:09:49][00:00:00][8524a2f2][ build:freedesktop-sdk.bst:components/fontconfig.bst] FAILURE Running commands
[11:09:49][--:--:--][8524a2f2][ build:freedesktop-sdk.bst:components/fontconfig.bst] START Caching artifact
[11:09:49][00:00:00][8524a2f2][ build:freedesktop-sdk.bst:components/fontconfig.bst] SUCCESS Caching artifact
[11:09:49][00:01:11][8524a2f2][ build:freedesktop-sdk.bst:components/fontconfig.bst] FAILURE Command failed
```

You can see that bst pulled a cached failure and promptly discarded it, but it then proceeded to get the failed action from the action cache and not actually retry the build.

Start by tracing the --retry-failed command-line path and the action-cache lookup used during remote execution. Reproduce the logged scenario with a failed cached action; done means retrying bypasses the cached failure and runs the build action again.

Written by the indexing model from the issue text.