fix: Changed 'equal_range()' + loop by 'find()' in resolveFirst() methods

[airween]

This PR fixes SonarCloud issues in these files:

• src/anchored_set_variable.cc
• src/collection/backend/in_memory-per_process.cc and one more place

Summary: AnchoredSetVariable and InMemoryCollection types are derived from std::unordered_multimap.

Both type has a resolveFirst(key) method (AnchoredSetVariable, InMemoryCollection), which finds the first occurrence of key in the collection.

The current implemented version uses equal_range() (doc) to find the key in a loop, and breaks from that after first match. This C++ collection has another method to find it where we don't need any loop, that's the find() (doc).

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[fzipi]

LGTM. I was looking if we can move the lock inside the if (before setting the value/expiration), but I guess the element found could be removed between the find step and the actual modification.