Promise queue interval started when not required

[tuliomir]

When running Jest locally without the automatic exit functionality, one process is kept open after the test finishes. Investigating this, @luislhl could find the following code:

hathor-wallet-lib/src/sync/gll.ts

Line 5 in a3962ab

const GLL = new PromiseQueue();

Which then instantiates a custom built interval:

hathor-wallet-lib/src/models/promise_queue.ts

Line 50 in a3962ab

this.#startInterval();

Since this code runs at the module root, any client importing the wallet-lib automatically runs this interval even if unneeded. This causes the issue with Jest testing, for example.

We should refactor this code in a way that this interval is only started when necessary.