Add functionality that allows bespoke benchmarks to be run under gitlab ci

Description

At the minute cron job gitlab runs are run on a 24 hour basis using a run token as a base point to work out what SHAs need testing. In certain circumstances it is necessary to run or re-run benchmarking tests for a given SHA range (e.g. corruption of results, failed tests). This MR adds functionality that allows tests to be run based on SHAs provided via build environment variables that can be either set via the online CI interface or can be scripted.

Changes proposed in this merge request:

• Add functionality to generate bespoke config test file.
• Add required logic to either bespoke or non bespoke test configuration generation.
• Update scripts to facilitate bespoke test running.
• Add cleanups for docker images and containers.
• Add option to write bespoke results to results cache.