Add support for summary files beyond year 2262

[berland]

Copied fallback code from res2df. Since #182 is stale, we duplicate the code from there.

Solves equinor/semeio#474

[codecov-commenter]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (392218d) 83.31% compared to head (f406f34) 83.49%.

❗ Current head f406f34 differs from pull request most recent head 7230f4e. Consider uploading reports for the commit 7230f4e to get more accurate results

Files	Patch %	Lines
src/fmu/ensemble/util/dates.py	96.07%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #238      +/-   ##
==========================================
+ Coverage   83.31%   83.49%   +0.17%     
==========================================
  Files          14       14              
  Lines        3026     3071      +45     
==========================================
+ Hits         2521     2564      +43     
- Misses        505      507       +2     

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[kwinkunks]

This looks great.