refactor: renaming module chunkmanager to fetch

[jeqo]

Now that purpose of chunkmanager module is more clear, we can rename it to fetch so it's explicit when it's used and regroup the components that belong to this module (specifically FetchChunkEnumeration that does not really belong in the transform module).

Changes:

• Renaming module to fetch
• Moving FetchChunkEnumeration from transform into fetch module
• Renaming cache configuration with fetch prefix

See commits for details.