Description of the change

Since this implementation does not traverse through an intermediary list multiple times, it is must faster.

Fixes the work described in this comment: #60 (comment)

Map
===
values
---------------
Map2a0bff.values: big map (1000000)
mean   = 2.89 s
stddev = 302.43 ms
min    = 2.52 s
max    = 3.43 s
M.values: big map (1000000)
mean   = 278.44 ms
stddev = 4.57 ms
min    = 271.75 ms
max    = 287.72 ms

Checklist:

• Added the change to the changelog's "Unreleased" section with a reference to this PR (e.g. "- Made a change (#0000)")
• Linked any existing issues or proposals that this pull request should close
• Updated or added relevant documentation
• Added a test for the contribution (if applicable)