The supervisor uses the following pattern for async module
initialization
```typescript
// module.ts
export const initialised = (async () => {
// do some async initialization
})();
// somewhere else
import * as module from 'module';
async function setup() {
await module.initialise;
}
```
The above pattern means that whenever the module is imported, the
initialisation procedure will be ran, which is an anti-pattern.
This converts any instance of this pattern into a function
```typescript
export const initialised = _.once(async () => {
// do some async initialization
});
```
And anywhere else on the code it replaces the call with a
```typescript
await module.initialised();
```
Change-type: patch
We are refactoring the supervisor test suite into unit tests (for
algorithms an domain model tests) and integration
tests (for interaction with out-of-process dependencies).
This means the current test suite needs to be classified into
these two categories, and fixed whenever possible.
This commit moves the test suite under the `test/legacy` folder, this
folder should be progressively migrated and eventually removed.
Subsequent commits will begin to split these files into unit and
integration whenever possible.
Depends-on: #1996
Change-type: patch
