Updated to work with Go 1.21

[BlakeOrth]

• Added OGRErr and CPLErr types to properly wrap the underlying C error types rather than reference the C errors directly. This allows methods to be defined on those types, which was a bug fix in Go 1.21
• Added type cast to all usages of the old C types

[codecov[bot]]

Codecov Report

Merging #22 (e8fdb80) into main (f8aa68a) will decrease coverage by 0.09%. The diff coverage is 3.24%.

@@           Coverage Diff            @@
##            main     #22      +/-   ##
========================================
- Coverage   5.03%   4.94%   -0.09%     
========================================
  Files          7       7              
  Lines       3020    3152     +132     
========================================
+ Hits         152     156       +4     
- Misses      2862    2990     +128     
  Partials       6       6              

Files Changed	Coverage Δ
algorithms.go	0.00% <0.00%> (ø)
ogr.go	0.21% <0.00%> (-0.01%)	:arrow_down:
osr.go	1.23% <0.45%> (-0.15%)	:arrow_down:
gdal.go	7.12% <2.32%> (-0.14%)	:arrow_down:
dataset.go	32.04% <33.33%> (+0.06%)	:arrow_up:

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