Make it easier to test lsm compiles correctly

[edvgui]

Context

I think it shows well that testing allocation properly is not an easy thing and knowing whether an observed misbehavior comes from the allocator plugin or the tests is not obvious.
I think we need to do the following things to avoid this type of issues in the future:

1. The allocation framework could be made more strict to fail when an allocation plugin is executed in a non validating compile.
2. We should provide meaningful examples on how to test allocation with the lsm_project fixture (this is independent of allocation v3 so it can be published already).
3. We should create a training about lsm allocation, and how it is bound to the lifecycle of a service.

Source: https://inmanta.slack.com/archives/C01QH7140NT/p1689152080989139

Actionable

• Update allocation mocked endpoints (v1 and v2) to explicitly check that the service has a candidate attribute set.
• Update compile method to assert (after the compile, when triggering a validation compile) that the state the service was in does have a state transfer starting from this state and with validation set to true.
• Improve the examples of tests to show how to properly test a lifecycle, and highlight in the tests (by the usage of inline comments) the important things to check

[sanderr]

For the third actionable, you can also actually highlight lines in code blocks.