ci: update artifact actions to v4

[joshuarli]

Uses artifacts/merge to merge together multiple artifacts from different jobs into the single one named github.sha that craft expects.

Summarily, upload-artifact v3 is deprecated but v4 doesn't support mutating an artifact with the name name by uploading different filepaths to the same artifact. Because we need a single artifact "github.sha", we have to use actions/merge to create it. Alternatively craft could be modified but this is the easiest way forward and I like the idea of a unified artifact, it makes craft simpler.

ref: getsentry/craft#552

[joshuarli]

as expected the final release artifact contains the 4 wheels and sdist:

$ unzip -l f3413bd18812984ca0dcf94adcf8b891ce1599c2.zip                                                                0
Archive:  f3413bd18812984ca0dcf94adcf8b891ce1599c2.zip
  Length      Date    Time    Name
---------  ---------- -----   ----
  1041231  09-23-2024 23:55   sentry_ophio-1.0.0-cp310-abi3-macosx_10_12_x86_64.whl
   991355  09-23-2024 23:55   sentry_ophio-1.0.0-cp310-abi3-macosx_11_0_arm64.whl
  4238356  09-23-2024 23:55   sentry_ophio-1.0.0-cp310-abi3-manylinux_2_17_aarch64.manylinux2014_aarch64.whl
  4331018  09-23-2024 23:55   sentry_ophio-1.0.0-cp310-abi3-manylinux_2_17_x86_64.manylinux2014_x86_64.whl
    26486  09-23-2024 23:55   sentry_ophio-1.0.0.tar.gz
---------                     -------
 10628446                     5 files

[armenzg]

You rock! Thanks for streamlining the upload of the repo!