git: openjdk/leyden: premain: Added "make bench" in all four framework demos; added relative performance numbers to premain/README.md

[duke]

Changeset: 04a95521
Author:    iklam <ilam3388 at gmail.com>
Date:      2024-04-23 16:29:39 +0000
URL:       https://git.openjdk.org/leyden/commit/04a95521fc88327e25cbe88cf62fa54ed8caa3b2

Added "make bench" in all four framework demos; added relative performance numbers to premain/README.md

! test/hotspot/jtreg/premain/README.md
! test/hotspot/jtreg/premain/lib/DemoSupport.gmk
+ test/hotspot/jtreg/premain/lib/GithubMDChart.java
! test/hotspot/jtreg/premain/spring-petclinic/Makefile