Functional test profiling with --perf (introduced in #14519) is currently broken, as TestNode._start_perf accesses the self.binary attribute which doesn't exist anymore since commit 0d2eefca8bf3cb64e3f2f912ed32118524430967 / PR #31866. Fix that by using the proper field self.binaries.paths.bitcoind.
Also, perf's error output for missing kernel permissions changed slightly in 2020 (s/tweaking/adjusting) (see https://github.com/torvalds/linux/commit/c1034eb069201f3f3c40f34f3d937ecb8049d0cf), so adapt our matching string as well in order to show the "couldn't collect data" warning if necessary. Relying on a certain output string is obviously brittle, so we might want to do something smarter there.
This is a minimum-diff-fix that works on my machine (arm64, Ubuntu 25.04, Kernel 6.17.0-8-qcom-x1e, perf 6.1.174). I think the feature is useful in principle, but considering that no one noticed for more than a year that it's broken, it seems that no one really uses it, and an alternative might also be to remove it. Curious to hear opinions.
