Use pickle's loads/dumps as a faster deepcopy

[kenodegard]

Description

Attempting to use pickle instead of deepcopy for a faster copy.

Split from:

• Miscellaneous render speedups #5225
• Speed up rendering by avoiding costly/redundant function calls #5248
• Remove duplicate extract_package_and_build_text call #5253

Checklist - did you ...

• Add a file to the news directory (using the template) for the next release's release notes?
• Add / update necessary tests?
• Add / update outdated documentation?

[codspeed-hq]

CodSpeed Performance Report

Merging #5281 will improve performances by 32.33%

_{Comparing kenodegard:pickle-vs-deepcopy (380a41c) with main (6982cbd)}

Summary

⚡ 1 improvements
✅ 2 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	kenodegard:pickle-vs-deepcopy	Change
⚡	test_pin_subpackage_benchmark	118.7 s	89.7 s	+32.33%

[beckermr]

My only comment here is as last time. If we encounter a data structure that does not pickle, we will get an error. It might be worth making a separate helper function with a try except block falling back to deepcopy.