Optimize the Maven Surefire JVM to speedup tests

[jtnord]

given we are forking the JVM for all the tests local testing (with several plugins) has shown that we can be much faster if we do not try and do expensive JIT compilation.
Also set the initial memory to the same as the maximum as this helps too.

This will not work if the JVM does not recognise the flags (they are available in hotspot in JDK7+) but other JVMs (j9?) are unknown about. that said the magority of plugin developers most likely use a hotspot based JVM and this is what we use in ci.jenkins.ci so I would recommend this and then let plugins whose authors build on something else adjust as nescessary.

[oleg-nenashev]

I am fine with that. Will work on AdoptOpenJDK also for the default engine

[jtnord]

J9 ignores the flags (tried with a bogus flag -XX:+sdkfjsdkfjsdf) so this should be (mostly) safe.

> java -XX:+sdkfjsdkfjsdf -showversion -jar jenkins-cli.jar --help
openjdk version "1.8.0_232"
OpenJDK Runtime Environment (build 1.8.0_232-b09)
Eclipse OpenJ9 VM (build openj9-0.17.0, JRE 1.8.0 Windows 10 amd64-64-Bit Compressed References 20191016_492 (JIT enabled, AOT enabled)
OpenJ9   - 77c1cf708
OMR      - 20db4fbc
JCL      - 97b5ec8f383 based on jdk8u232-b09)

Neither -s nor the JENKINS_URL env var is specified.
Jenkins CLI
Usage: java -jar jenkins-cli.jar [-s URL] command [opts...] args...
Options:
-s URL       : the server URL (defaults to the JENKINS_URL env var)
-http        : use a plain CLI protocol over HTTP(S) (the default; mutually exclusive with -ssh and -remoting)
-ssh         : use SSH protocol (requires -user; SSH port must be open on server, and user must have registered a public key)
-remoting    : use deprecated Remoting channel protocol (if enabled on server; for compatibility with legacy commands or command modes only)
-i KEY       : SSH private key file used for authentication (for use with -ssh or -remoting)
-p HOST:PORT : HTTP proxy host and port for HTTPS proxy tunneling. See https://jenkins.io/redirect/cli-https-proxy-tunnel
-noCertificateCheck : bypass HTTPS certificate check entirely. Use with caution
-noKeyAuth   : dont try to load the SSH authentication private key. Conflicts with -i
-user        : specify user (for use with -ssh)
-strictHostKey : request strict host key checking (for use with -ssh)
-logger FINE : enable detailed logging from the client
-auth [ USER:SECRET | @FILE ] : specify username and either password or API token (or load from them both from a file);
for use with -http, or -remoting but only when the JNLP agent port is disabled

The available commands depend on the server. Run the help command to
see the list.