Update copyright headers

[ptagl]

This pull request introduces the following changes:

• a new Python script update-copyright-headers.py to update copyright headers in the source files of the repository
• updated headers for "Zen Blockchain Foundation" for all the files modified between 2018-01-18 and 2023-09-27
• updated headers for "The Horizen Foundation" for all the files modified between 2023-09-28 and 2024-05-19

The previous script fix-copyright-headers.py has been removed and the devtools readme has been updated accordingly.

[ptagl]

@drgora I've added a basic mechanism to exclude commits that we shouldn't take into account when updating copyright headers (like the updates of the copyright headers themselves)! 😄

The mechanism is based on a new --exclude-commit argument (list) with the following behavior:

• if the argument is empty (not provided by the user), the script tries to automatically exclude commits containing update-copyright-headers.py inside the message or copyright inside the summary (I didn't want to check the whole message here just to prevent accidental exclusion of relevant commits); after the automatic detection, user is asked to confirm that the list of commits is fine, with the possibility to continue, abort or ignore the list
• if the list is provided by the user, no automatic detection is performed

Let me know what you think about it.

Thanks!

[drgora]

@drgora I've added a basic mechanism to exclude commits that we shouldn't take into account when updating copyright headers (like the updates of the copyright headers themselves)! 😄

The mechanism is based on a new --exclude-commit argument (list) with the following behavior:

* if the argument is **empty** (not provided by the user), the script tries to automatically exclude commits containing `update-copyright-headers.py` inside the message or `copyright` inside the summary (I didn't want to check the whole message here just to prevent accidental exclusion of relevant commits); after the automatic detection, user is asked to confirm that the list of commits is fine, with the possibility to continue, abort or ignore the list

* if the list is **provided** by the user, no automatic detection is performed

Let me know what you think about it.

Thanks!

Sounds great to me, thanks!