Store HW Specific Benchmark Variables for Perf Testing

Currently, for internal testing, we are using `master_machine_list.xml`, a file that has info about all machines regarding their HW and specific benchmark variables, with PerfNext to dynamically populate HW specific benchmark variables. We would need a similar file for enabling perf testing on AdoptOpenJDK.

### Some Options for Storing HW Specific Benchmark Variables

### 1) Use Environment Variables for Jenkins Node

`https:///computer//api/`

**Pros:** 1) Everything in one place 2) Can possibly be integrated with the new machines data file generated from openjdk-jenkins-helper for PerfNext: https://github.com/AdoptOpenJDK/openjdk-jenkins-helper/issues/25 3) PerfNext and Openjdk-tests Framework can use just one file that has all info about the machine and the HW specific benchmark variables

**Cons:** 1) Hacky! We won't really be using the environment vars as expected. Instead of using the vars in bash (i.e. $VAR_NAME), we'll be storing the XML data and parsing that. 2) "Agent Config History" doesn't keep track of changes for environment vars. 3) Not friendly UI to edit configs

### 2) Use some existing Git Repo

**Pros:** 1) Clean approach 2) Git takes care of versioning 3) Can be easily edited

**Cons:** 1) Won't integrate with the new machines data file generated from openjdk-jenkins-helper for PerfNext: https://github.com/AdoptOpenJDK/openjdk-jenkins-helper/issues/25 2) PerfNext and Openjdk-tests Framework would need to use 2 separate files instead of just one that has all the info about the machine and the HW specific benchmark variables

Start by reviewing master_machine_list.xml and the Jenkins node API approach described in the issue, then compare them with the openjdk-jenkins-helper issue 25 integration. The work is done when a storage approach is selected and AdoptOpenJDK perf testing can obtain hardware-specific benchmark variables for both PerfNext and the OpenJDK tests framework.

Written by the indexing model from the issue text.