Add a configurable memory limit to the torrent repository and implement dashmap [#567, #565]

[mickvandijke]

Closes https://github.com/torrust/torrust-tracker/issues/567 Closes https://github.com/torrust/torrust-tracker/issues/565

[mickvandijke]

Needs rebase and commit cleanup first before reviewing.

[josecelano]

Hi @mickvandijke what is the status of this PR? Maybe:

• Rebase
• And https://github.com/torrust/torrust-tracker/issues/646

By the way, why did you use deepsize?

I'm just curious, I've found this one https://github.com/str4d/memuse

[josecelano]

Hi @mickvandijke I'm closing this PR:

• The Dashmap was already implemented.
• The memory limit should be implemented for all repos or not implemented at all.