swift

66fec882 - Update stdlib DocC curation for 6.4 symbols (cherry-pick from main to release/6.4.x). (#92858)

Update stdlib DocC curation for 6.4 symbols (cherry-pick from main to release/6.4.x). (#92858) [Cherry-pick #92405 from main to release/6.4.x] This PR updates files in the `stdlib.docc` directory to provide curation for symbols added to the standard library in release 6.4, including task cancellation shields and refs. The [stdlib documentation on docs.swift.org](https://docs.swift.org/latest/documentation/swift) uses these files to organize the online documentation into topics. This PR doesn't affect any compilable source. It's only for the use of the `docc` compiler to produce documentation, either in swift.org's CI or if someone wants to generate a local copy. rdar://181594680 - **Explanation**: Updates the .md files in the `stdlib.docc` directory so that documentation on swift.org properly organizes new topics. - **Scope**: The changes are entirely within markdown files and are not compiled as part of building Swift or the standard library. - **Issues**: rdar://181594680 - **Original PRs**: #92405 - **Risk**: None. This only affects documentation. - **Testing**: None needed. This doesn't affect compiled code. The resulting documentation has been built locally and can be previewed with GitHub pages here: https://invalidname.github.io/stdlib-docs-preview/documentation/swift - **Reviewers**: - @heckj