Port of aggdraw to agg 2.4

[djhoese]

This is a rewrite/redo of #50 which was a redo of #48. After having this merged into main it was made apparent that the results produced by agg 2.4 inside aggdraw were not close enough to what was previously produced. Enough time had gone by that I thought "oh I'll just fix it eventually and then make a release"...

Well that never happened so I recently moved the maint/1.3 branch back to main and am now recreating this migration to agg 2.4 based on that new main branch. This was accomplished by cherry-picking 4 of the commits from #50.

TODO: I still need to review changes that were made to main after #50 was merged but were not backported to the maint/1.3 branch. These currently only live in the feat-agg24 branch on the pytroll/aggdraw repository. These PRs include:

• Change default linejoin and linecap to preserve previous behavior #62 for linejoin and linecap but this was to address differences in agg 2.4
• Don't use deprecated distutils module. #87
• Use array delete for point arrays #60
• Need to verify Add rounded_rectangle method #78's behavior is now equivalent to what was ported in Backport rounded_rectangle to maintenance branch #102. Given the weird git history it is possible a change made after Port of aggdraw to agg 2.4 #50 that was respected in Add rounded_rectangle method #78 was not needed in Backport rounded_rectangle to maintenance branch #102 and is now not in this PR.
• Biggest thing is that Resolve differences after agg 2.2 and agg 2.4 migration #67 needs to be resolved

All other changes since #50 seem to have been ported or are CI/maintenance related.

[djhoese]

Ok #60 was re-added to main in #114. #87 and #78 were already backported. So now the only thing remaining (I think) is for me to rebase this PR to include #114 and then make it produce equivalent results. However, after a rebase I'm in no rush to fix the differing results.

[djhoese]

@benburrill My latest commit changes the use of add_path from your newest rounded rectangle PR to concat_path which matches your old rounded_rectangle PR. Does that sound right to you?

[benburrill]

For agg 2.4, yes. I changed it to add_path for the agg 2.2 backport because it didn't compile with concat_path.