[Filebeat] Unable to set noexec on /tmp

[michel-laterman]

Users are currently unable to set noexec on /tmp for a *nix OS as filebeat diagnostics use the OS's default temp directory when gathering the registry.
See

beats/filebeat/beater/diagnostics.go

Line 78 in 0678f4d

f, err := os.CreateTemp("", "filebeat-registry-*.tar")

We should change this to a directory that can be supplied through some other means.
For the elastic-agent we have paths.TempDir, we should use something similar for this creation call.

[elasticmachine]

Pinging @elastic/elastic-agent-control-plane (Team:Elastic-Agent-Control-Plane)

[michel-laterman]

Agent PR that fixes a similar issue: elastic/elastic-agent#8472

[michel-laterman]

Just as a note setting $TMPDIR will control where this file is created; this issue can be regarded as low-priority as we have a work-around.