chore: update go version 1.26.5 (#6631)
Go 1.26.5 fixes CVE-2026-39822: on Unix, os.Root improperly followed a
trailing-slash symlink in the final path component (e.g. Open("link/")),
allowing a path to escape the root. The 1.26 line is affected from
1.26.0 up to, but not including, 1.26.5.
Bumps the go directive across the root module and every submodule, plus
the golang builder image (tag and digest) in Dockerfile.standalone,
e2e/Dockerfile and tilt.debug.dockerfile so the shipped binaries are
built with the patched toolchain.
Signed-off-by: Alexander Chernov <alexander@chernov.it>