iovec-util: introduce iovec_equal(), and add overflow check (#41700)

diff --cc src/core/namespace.c
Simple merge

diff --cc src/cryptenroll/cryptenroll-tpm2.c
Simple merge

diff --cc src/import/pull-job.c
Simple merge

diff --cc src/shared/dissect-image.c
Simple merge

diff --cc src/shared/tpm2-util.c
Simple merge

diff --cc src/sysupdate/sysupdate-resource.c
Simple merge