fix: [SUP-1093] Replaced manual pMap with actual pMap

[dotkas]

What does this PR do?

A while back we introduced some pseudo-parallelization (to the extend Node allows) of promises when sending requests to our backend. The solution sped up things a bit, but the Promise-chunk would wait until the slowest promise had finished before starting a new batch.

pMap accounts for this problem. The performance increase will not be that significant for smaller chunks of requests, but for bigger ones the lack of holes in the chain of unbroken ought to speed things up a bit.

This change (like the one before) comes on the back of another customer support ticket, where scanning a large project takes over an hour.

The bottlenecks are numerous, but one of the biggest, as far as I have been able to identify, reveals itself around the requests to vulndb.

Performance comparisons

Comparing the performance running locally on an M1 Macbook Pro, against Snyk CLI v. 1.1159.0.

time snyk test --yarn-workspaces --detection-depth=3

Solution	Projects	Runtime
Previous	72	32m
This one	72	25m

Still quite a way to go to get this down to a few minutes, but I guess it's a start.

[github-actions]

	Warnings
⚠️	You've modified files in src/ directory, but haven't updated anything in test folder. Is there something that could be tested?
⚠️	"fix: replaced manual pMap with actual pMap, so not to wait for all promises to finish before moving on" is too long. Keep the first line of your commit message under 72 characters.

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