Add multi-threading for pack/unpack

[cr3ativ3cod3r]

Description

This PR introduces parallel processing of pack and unpack operations. Previously the layers were packed and unpacked sequentially.

• In savekitfilelayers, calls to savecontentlayer is now executed in a new goroutine. They are also indexed, so that the order of layers is preserved.
• In unpackrecursive, calls to unpacklayers is now executed in a new goroutine.
• For the progress bars, created an instance of mpb.Progress and each goroutine adds a bar to this shared instance.
• In ignorepaths struct, added a mutex and used it in matches method as MatchesOrParentMatches is not safe for concurrent access.

Linked issues

closes #254

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