FIX: Select function in segmentation resampling workflow

[mgxd]

The segmentation selection code was a bit convoluted, this addresses the following:

• Adding a mapping for common replacements
• Avoiding string iteration
• Stopping iteration over files upon the first match
• Raising FileNotFoundError, rather than an unclear IndexError, if no matches are found.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 93.75000% with 1 line in your changes missing coverage. Please review.

Project coverage is 66.71%. Comparing base (f368a28) to head (4738420). Report is 6 commits behind head on master.

Files	Patch %	Lines
smriprep/workflows/surfaces.py	91.66%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #450 +/- ## ========================================== + Coverage 66.36% 66.71% +0.35% ========================================== Files 31 31 Lines 2072 2076 +4 Branches 249 246 -3 ========================================== + Hits 1375 1385 +10 + Misses 696 690 -6 Partials 1 1 ```

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[mgxd]

@effigies can we sneak this into a patch release, or will it require a new minor?

[effigies]

I'm okay with a patch release. The workflow cache invalidation is straightforward here.