chore(ci): strip CI to op-reth testing essentials (#17)

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**Description**

Merges down and cleans up changes to ci from isthmus-devnet-0 branch.
Ref #8.

- Removes jobs: for L1, for deploying, some maintenance jobs
- Removes cron jobs

**Tests**

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.github/workflows/bench.yml

@@ -1,11 +1,7 @@
 # Runs benchmarks.
 
 on:
-  pull_request:
-  # TODO: Disabled temporarily for https://github.com/CodSpeedHQ/runner/issues/55
-  # merge_group:
-  push:
-    branches: [main]
+  workflow_dispatch:
 
 env:
   CARGO_TERM_COLOR: always