Use One Pass in Duration Parsing

[pavelbrm]

Summary

This PR speeds up the ISO duration parsing by ~200ns (did benchmark the change).

Previously the code would run the regexp twice against the same string - one to determine whether where is a match, and then to get the actual match. Under the hood, both methods use the same low level implementation, and FindStringSubmatch is also capable of indicating whether there was a match. Namely, if the result of a call to FindStringSubmatch was strictly nil, that means no matches found. Hence the change – match a given string against the pattern only once.

This is a follow up to #1865.

Type of Change

• Product feature
• Bug fix
• Performance improvement
• Refactor
• Other

Tested Environments

• Development
• Staging
• Production

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