fix(remappings): properly filter only autodetected remappings, do not sort unnecesarily

[Evalir]

Motivation

Closes #5561.

The issue highlighted a few edge cases:

• we should filter with starts_with, rather than contains
• we should only filter autodetected remappings, instead of all remappings (as it might be intended for the user to have several keys pointing to the same location)
• we should filter without sorting, so filter instead of deduping.

Solution

• Adds an into_inner method to the wrapper which produces a vector of remappings that are unique.
• removes unwanted sorting/filtering

[mattsse]

few nits,

would like an integration test for forge remappings with remappings.txt