ci: Enable experimental kernel stuff in i686 task

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

IPC remains explicitly disabled.

.github/workflows/ci.yml

@@ -492,7 +492,7 @@ jobs:
             timeout-minutes: 120
             file-env: './ci/test/00_setup_env_native_nowallet_libbitcoinkernel.sh'
 
-          - name: 'no IPC, i686, DEBUG'
+          - name: 'i686, no IPC'
             cirrus-runner: 'ghcr.io/cirruslabs/ubuntu-runner-amd64:24.04-md'
             fallback-runner: 'ubuntu-24.04'
             timeout-minutes: 120