refactor: Improvements in Entry.resolveLinks

[gmoraleda]

Summary

This PR aims at improving the speed of the resolveLinks function.

• Moved casting to [Link] to the first swift statement.
• Moving to the next item if the array of links does not require resolution or is cached.
• Caching the array of resolved links after processing them.

Also

• Corrected typos here and there
• Extracted nested function inside sync for fetching types -> handleContentTypeFetch

Discussion

The observed sync times using the space p557f7qi815g went from around 8 seconds to the lower end of the 7 seconds.
Still a marginal gain but a small improvement in any case.