[JENKINS-39369] Automatically dump agent logs to the disk - Jenkins Jira

In Jenkins common SSH and JNLP slaves do not dump logs to the disk by default. It complicates the analysis of connectivity issues.

Requirements:

After specifying an option, remoting starts forwarding its logs to the disk
Logs are being put to a special directory, which may potentially contain additional files
By default Jenkins should not enable this directory since there are many potential compatibility issues (alternative - create it in the .jenkins directory with a kind of unique ID for the remoting instance)
Nice2Have: These logs can be rotated easily using internal settings or external mechanisms

is blocked by

JENKINS-39370 Introduce the remoting working directory concept

is duplicated by

JENKINS-517 Collect logs on slaves to the master

is related to

JENKINS-38520 Every message in agent log appears twice with the -agentLog option

JENKINS-39817 Java web start should also provide the "-agentLog" parameter

links to

remoting/pull/129