ci/ci-tron: switch to the upstream ci-tron template

Up until now, every project using CI-Tron had to write their own job
submission flow because CI-Tron itself was not providing any official
way of interacting with it via GitLab.

This however changed, and the solution is vastly superior to what we
have been using in Mesa:

 * Ability to pass all the environment variables of the job to the DUT,
   so no need to remember to add variables in
   `export-gitlab-job-env-for-dut.sh` anymore

 * No dependency on Mesa code, which means no need to wait on
   python-artifacts and the ability to replicate a run by just copying
   the job description outputted by the job \o/

 * Ability to have as many initrd, HTTP, and TFTP artifacts as wanted

 * Ability to expose a variable through a TFTP/HTTP endpoint or as an
   initrd

 * Ability to overwrite the platform environment (machine-specific FW)

 * Ability to have as many kernel cmdline variables, all merged when
   generating the final cmdline. This makes it easy to share some
   snippets of cmdline between jobs

Transitioning from the custom to the generic template is however pretty
involved. This commit does the minimum changes needed to switch to the
new model, often simply replacing the B2C_ prefix with CI_TRON_.

Further renaming of "b2c" prefixes into "ci-tron" is left for future
commits.

Co-authored-by: Eric Engestrom <eric@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34795>

.gitlab-ci/common/export-gitlab-job-env-for-dut.sh

@@ -1,7 +1,6 @@
 #!/bin/bash
 
 VARS=(
-    ACO_DEBUG
     ANGLE_TAG
     ANGLE_TRACE_FILES_TAG
     ANV_DEBUG
@@ -114,9 +113,6 @@ VARS=(
     PIGLIT_TRACES_FILE
     PIPELINE_ARTIFACTS_BASE
     RADEON_DEBUG
-    RADV_DEBUG
-    radv_enable_float16_gfx8
-    RADV_PERFTEST
     S3_HOST
     S3_JWT_FILE
     S3_RESULTS_UPLOAD
@@ -126,7 +122,6 @@ VARS=(
     VIRGL_HOST_API
     VIRGL_RENDER_SERVER
     VK_DRIVER
-    vk_require_etc2
     WAFFLE_PLATFORM
     ZINK_DEBUG
     ZINK_DESCRIPTORS