CI, TST: simplified automated build script + CI workflows

[shanedsnyder]

• Add new build script build-darshan.sh intended to simplify building/testing of darshan-runtime and darshan-util in some of our automated testing frameworks. You can provide the following env vars to control some aspects of the build:
  • DARSHAN_INSTALL_PREFIX - path to install Darshan
  • DARSHAN_LOG_PATH - formatted path to store Darshan logs
  • DARSHAN_RUNTIME_CONFIG_ARGS - darshan-runtime config args
  • DARSHAN_UTIL_CONFIG_ARGS - darshan-util config args
  • DARSHAN_RUNTIME_SKIP - skip darshan-runtime build if set
• Updated GitHub workflows and cibuildwheel process to use this script
• Removed old automated testing scripts for building Darshan, which were tied to a Jenkins plugin and less flexible.
• Removed now decomissioned ALCF Theta regression testing environment
• Updated Python test case to account for new build directory organization from this new script.