Update and Standardize Copyrights

[drewroberts]

This PR updates copyrights from 2023 to 2024 for "The Bitcoin Core developers" and "Bitcoin Developers" while leaving copyrights for other entities alone. It also standardizes the use of copyrights as there were approximately 20 files that said "-present" while hundreds said "-2023" or another end year that hadn't been updated. Although this is a trivial change, a significant number of files were edited, so please thoroughly review before merging. I double-checked every edit I made but would appreciate your feedback.

2024 is here and we're less than a month away from the halving!

[DrahtBot]

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[achow101]

-present is intentional and it's purpose is to avoid having to update the copyright headers every year, and also so we can avoid constantly getting PRs such as this.

Besides that, the copyright year notice is typically updated at the end of the year being added, and is only done to files that were changed within that year. But I think we're probably going to stop doing that now too. It's kinda pointless.

[drewroberts]

That makes sense. Thank you for taking the time to explain the procedure to me, @achow101