Update CODEOWNERS: Aug 2026 (#24847)

As a follow-up on bff05a9d, fill in the current Codeowners file with TSC
members, as well as nominate additional reviewers.

Contributors who are removed from the list for large scopes: the
proposal makes a loose assumption that they are no longer actively
developing and/or reviewing the affected segments of the codebase. Thus,
the PR should only go in once it satisfies edit requests and a general
approval by such long-standing contributors and code owners.

There's little to no fine-graining of directory scopes in this PR. A
handful of directories is removed from the list as either outdated or as
a way of (temporarily?) transfering the default code ownership thereof
to higher-level code owners.
Any contributor, regardless of TSC membership, is generally free to
volunteer for the existing or narrower review scopes, as well as offload
notifications and first-point-of-contact duties to other project
members.

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Signed-off-by: Artem Gindinson <gindinson@roofline.ai>