CLN: Refactor ecl scanning to use resfo

[mferrera]

Resolves #838

Some benchmarks

# xtgeo-testdata/3dgrids/simpleb8/E100_3LETTER_TRACER.UNRST - 1.01 MB
OLD: tests/test_grid3d/test_grid_properties.py::test_scan_dates Dates scanned in 0.0027261669747531414 seconds
NEW: tests/test_grid3d/test_grid_properties.py::test_scan_dates Dates scanned in 0.002314541954547167 seconds

# xtgeo-testdata/3dgrids/reek/REEK.UNRST - 42.4 MB
OLD: tests/test_grid3d/test_grid_properties.py::test_scan_dates Dates scanned in 0.015472916886210442 seconds
NEW: tests/test_grid3d/test_grid_properties.py::test_scan_dates Dates scanned in 0.06493925000540912 seconds

# xtgeo-testdata/3dgrids/bench_spe9/BENCH_SPE9.UNRST - 90.7 MB
OLD: tests/test_grid3d/test_grid_properties.py::test_scan_dates Dates scanned in 0.0327368329744786 seconds
NEW: tests/test_grid3d/test_grid_properties.py::test_scan_dates Dates scanned in 0.055844167014583945 seconds

This is a limited data set but it looks like resfo may not slow down as quickly as the C code relative to the file size.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (8e46e37) 79.94% compared to head (1675a88) 79.92%. Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1078 +/- ## ========================================== - Coverage 79.94% 79.92% -0.02% ========================================== Files 94 94 Lines 13570 13532 -38 Branches 2248 2242 -6 ========================================== - Hits 10848 10815 -33 + Misses 1977 1975 -2 + Partials 745 742 -3 ```

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