Enables co-locating multiple tasks in a given work-set.
Tasks are bucketed by the following:
* OS
* job id
* setup container
* VM SKU & image (used in pre-1.0 style tasks)
* pool name (used in 1.0+ style tasks)
* if the task needs rebooting after the task setup script executes.
Additionally, a task will end up in a unique bucket if any of the following are true:
* The task is set to run on more than one VM
* The task is missing the `task.config.colocate` flag (all tasks created prior to this functionality) or the value is False
This updates the libfuzzer template to make use of colocation. Users can specify co-locating all of the tasks *or* co-locating the secondary tasks.
When running libfuzzer in 'fuzzing' mode, we expect the following on exit.
If the exit code is zero, crashing input isn't required. This happens if the user specifies '-runs=N'
If the exit code is non-zero, then crashes are expected. In practice, there are two causes to non-zero exits.
1. If the binary can't execute for some reason, like a missing prerequisite
2. If the binary _can_ execute, sometimes the sanitizers are put in such a bad place that they are unable to record the input that caused the crash.
This PR enables handling these two non-zero exit cases.
1. Optionally verify the libfuzzer target loads appropriately using `target_exe -help=1`. This allows failing faster in the common issues, such a missing prerequisite library.
2. Optionally allow non-zero exits without crashes to be a warning, rather than a task failure.
1. Merge 'create' and 'update' to a single 'save' operation.
2. Allow fetching a single template.
This enables the following workflow:
```
$ onefuzz job_templates manage get libfuzzer_linux > template.json
$ <... update template as desired ...>
$ onefuzz job_templates manage save libfuzzer_linux @./template.json
$
```
