Remove deprecated _ec_privkey_{negate,tweak_add,tweak_mul} aliases from API #1593

1. 
   theStack commented at 11:46 pm on August 20, 2024: contributor

   These function aliases have been described as DEPRECATED in the public API docs already many years ago (see #701, commit 41fc7856), and in addition explicit deprecation warnings are shown by the compiler at least since the first official release 0.2.0 (see PR #1089, commit fc94a2da), so it should be fine to just remove them by now without causing bad surprises to any users.

   Note that this PR intentionally doesn’t include other deprecated flags/types/aliases by now, as they all have been introduced or marked as deprecated later (though the compiler deprecation warnings have been introduced at the same time). There are no deprecation rules yet and seemingly no removal of deprecated types/functions has ever happened so far, so it might make sense to discuss how to handle deprecation in general and introduce guidelines in the future.

2. Remove deprecated _ec_privkey_{negate,tweak_add,tweak_mul} aliases

   These function aliases have been described as DEPRECATED in the public
   API docs already many years ago (see #701, commit 41fc7856), and in
   addition explicit deprecation warnings are shown by the compiler at
   least since the first official release 0.2.0 (see PR #1089, commit
   fc94a2da), so it should be fine to just remove them by now.

   5ce9b577f9

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