crate-header: Fix deprecation warnings

[eth3lbert]

This PR addresses deprecation warnings by explicitly loading async values (crate.keywords, crate.owner_user) using tasks.

This should hopefully resolve some deprecation warnings similar to the following:

{"type":"warn","text":"DEPRECATION: Do not use A() on an EmberData PromiseManyArray [deprecation id: ember-data:no-a-with-array-like] This will be removed in ember-data 5.0.\n        at logDeprecationStackTrace (http://localhost:7357/assets/vendor.js:712:308)\n        at HANDLERS.<computed> (http://localhost:7357/assets/vendor.js:667:339)\n        at raiseOnDeprecation (http://localhost:7357/assets/vendor.js:715:210)\n        at HANDLERS.<computed> (http://localhost:7357/assets/vendor.js:667:339)\n        at eval (webpack://crates-io/../../.pnpm/@ember+test-helpers@4.0.4_@babel+core@7.26.0_ember-source@6.0.1_@glimmer+component@2.0.0_rsvp@4.8.5_webpack@5.97.1_/node_modules/@ember/test-helpers/dist/setup-context-Cx9HkMuO.js?:560:8)\n        at HANDLERS.<computed> (http://localhost:7357/assets/vendor.js:667:339)\n        at invoke (http://localhost:7357/assets/vendor.js:667:501)\n        at deprecate (http://localhost:7357/assets/vendor.js:772:442)\n        at deprecate$1 (http://localhost:7357/assets/vendor.js:968:335)"}
{"type":"warn","text":"DEPRECATION: The findBy method on ember-data's PromiseManyArray is deprecated. await the promise and work with the ManyArray directly. [deprecation id: ember-data:deprecate-promise-many-array-behaviors] This will be removed in ember-data 5.0.\n        at logDeprecationStackTrace (http://localhost:7357/assets/vendor.js:712:308)\n        at HANDLERS.<computed> (http://localhost:7357/assets/vendor.js:667:339)\n        at raiseOnDeprecation (http://localhost:7357/assets/vendor.js:715:210)\n        at HANDLERS.<computed> (http://localhost:7357/assets/vendor.js:667:339)\n        at eval (webpack://crates-io/../../.pnpm/@ember+test-helpers@4.0.4_@babel+core@7.26.0_ember-source@6.0.1_@glimmer+component@2.0.0_rsvp@4.8.5_webpack@5.97.1_/node_modules/@ember/test-helpers/dist/setup-context-Cx9HkMuO.js?:560:8)\n        at HANDLERS.<computed> (http://localhost:7357/assets/vendor.js:667:339)\n        at invoke (http://localhost:7357/assets/vendor.js:667:501)\n        at deprecate (http://localhost:7357/assets/vendor.js:772:442)\n        at deprecate$1 (http://localhost:7357/assets/vendor.js:968:335)"}
{"type":"warn","text":"DEPRECATION: The `findBy` method on the class ManyArray is deprecated. Use the native array method `find` instead. [deprecation id: ember-data:deprecate-array-like] This will be removed in ember-data 5.0.\n        at logDeprecationStackTrace (http://localhost:7357/assets/vendor.js:712:308)\n        at HANDLERS.<computed> (http://localhost:7357/assets/vendor.js:667:339)\n        at raiseOnDeprecation (http://localhost:7357/assets/vendor.js:715:210)\n        at HANDLERS.<computed> (http://localhost:7357/assets/vendor.js:667:339)\n        at eval (webpack://crates-io/../../.pnpm/@ember+test-helpers@4.0.4_@babel+core@7.26.0_ember-source@6.0.1_@glimmer+component@2.0.0_rsvp@4.8.5_webpack@5.97.1_/node_modules/@ember/test-helpers/dist/setup-context-Cx9HkMuO.js?:560:8)\n        at HANDLERS.<computed> (http://localhost:7357/assets/vendor.js:667:339)\n        at invoke (http://localhost:7357/assets/vendor.js:667:501)\n        at deprecate (http://localhost:7357/assets/vendor.js:772:442)\n        at deprecate$1 (http://localhost:7357/assets/vendor.js:968:335)"}

[Turbo87]

looks good to me at first glance. I guess technically, if the list of keywords/owners changes while looking at this page it won't get updated, but I don't think that is realistically a problem :D