Update Trillium to Rocq 9.0 and latest Iris / stdpp#8

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fresheed wants to merge 17 commits intomainfrom

update_trillium

Commits on Jun 3, 2025

left only "trillium" dir and bumped to coq 9.0
fresheed
committed

Commits on Jun 10, 2025

made it build and install
fresheed
committed

Commits on Jun 13, 2025

Commits on Jun 26, 2025

specified the current version of Trillium (quite arbitrary)
fresheed
committed

Commits on Aug 29, 2025

Commits on Aug 31, 2025

restored fairis up to examples
fresheed
committed

Commits on Sep 21, 2025