[red-knot] pull primer projects to run from file (#17473)

## Summary

The long line of projects in `mypy_primer.yaml` is hard to work with
when adding projects or checking whether they are currently run. Use a
one-per-line text file instead.

## Test Plan

Ecosystem check on this PR.

.github/workflows/mypy_primer.yaml

@@ -52,6 +52,8 @@ jobs:
         run: |
           cd ruff
 
+          PRIMER_SELECTOR="$(paste -s -d'|' crates/red_knot_python_semantic/resources/primer/good.txt)"
+
           echo "new commit"
           git rev-list --format=%s --max-count=1 "$GITHUB_SHA"
 
@@ -62,13 +64,14 @@ jobs:
 
           cd ..
 
+          echo "Project selector: $PRIMER_SELECTOR"
           # Allow the exit code to be 0 or 1, only fail for actual mypy_primer crashes/bugs
           uvx mypy_primer \
             --repo ruff \
             --type-checker knot \
             --old base_commit \
             --new "$GITHUB_SHA" \
-            --project-selector '/(mypy_primer|black|pyp|git-revise|zipp|arrow|isort|itsdangerous|rich|packaging|pybind11|pyinstrument|typeshed-stats|scrapy|werkzeug|bidict|async-utils|python-chess|dacite|python-htmlgen|paroxython|porcupine|psycopg)$' \
+            --project-selector "/($PRIMER_SELECTOR)\$" \
             --output concise \
             --debug > mypy_primer.diff || [ $? -eq 1 ]
 

crates/red_knot/docs/mypy_primer.md

@@ -31,7 +31,7 @@ mypy_primer \
 ```
 
 This will show the diagnostics diff for the `black` project between the `main` branch and your `my/feature` branch. To run the
-diff for all projects, you currently need to copy the project-selector regex from the CI pipeline in `.github/workflows/mypy_primer.yaml`.
+diff for all projects we currently enable in CI, use `--project-selector "/($(paste -s -d'|' crates/red_knot_python_semantic/resources/primer/good.txt))\$"`.
 
 You can also take a look at the [full list of ecosystem projects]. Note that some of them might still need a `knot_paths` configuration
 option to work correctly.

crates/red_knot_python_semantic/resources/primer/good.txt

@@ -0,0 +1,23 @@
+arrow
+async-utils
+bidict
+black
+dacite
+git-revise
+isort
+itsdangerous
+mypy_primer
+packaging
+paroxython
+porcupine
+psycopg
+pybind11
+pyinstrument
+pyp
+python-chess
+python-htmlgen
+rich
+scrapy
+typeshed-stats
+werkzeug
+zipp