ci: Enable experimental kernel stuff in G++-12 task (previous releases)

Base the task on --preset=dev-mode to ensure maximal coverage and add
the following:

   bitcoin-chainstate (experimental) ... ON
   libbitcoinkernel (experimental) ..... ON
   kernel-test (experimental) .......... ON

Also, shorten the name, for a less cluttered web view.

.github/workflows/ci.yml

@@ -510,7 +510,7 @@ jobs:
             timeout-minutes: 240
             file-env: './ci/test/00_setup_env_native_fuzz_with_valgrind.sh'
 
-          - name: 'previous releases, depends DEBUG'
+          - name: 'previous releases'
             cirrus-runner: 'ghcr.io/cirruslabs/ubuntu-runner-amd64:24.04-md'
             fallback-runner: 'ubuntu-24.04'
             timeout-minutes: 120