chore: prepare 2.12.0 (#5070)

* chore: prepare 2.12.0

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* docs: more info on numpy 2

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* docs: mention NumPy 2 in README

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* docs: add release date

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* docs: add 4955

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* Update changelog.rst

* docs: address review comments

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

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Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>