chore: merge CI linting jobs (#5904)

* chore: merge CI linting jobs

* Merge the `markdown-lint-check` step into `lint`

* Rename `coder.yaml` to `ci.yaml`

* Improve casing of security workflow

* Remove unused workflows and merge into contrib

* Format ci.yaml

* Fix CodeQL language

* Fix github action name

.github/workflows/dependabot.yaml

@@ -1,13 +0,0 @@
-# Dependabot is annoying, but this makes it a bit less so.
-name: Auto Approve Dependabot
-
-on: pull_request_target
-
-jobs:
-  auto-approve:
-    runs-on: ubuntu-latest
-    permissions:
-      pull-requests: write
-    steps:
-      - uses: hmarr/auto-approve-action@v3
-        if: github.actor == 'dependabot[bot]'