chore: remove and ignore intermediate snapshots integration test snapshots (#22731)

When running integration tests, they are executed inside an intermediate directory named `cdk-integ.out.*`. These files should never be committed to version control. This change removes the last few accidentally committed files, and adds a global gitignore rule to prevent any files being added in future.

The unit tests for `integ-runner` rely on these (fake) intermediate artifacts for assertions, so they are still included. However these aren't real integreation tests anyway.

----

### All Submissions:

* [x] Have you followed the guidelines in our [Contributing guide?](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md)

### Adding new Unconventional Dependencies:

* [ ] This PR adds new unconventional dependencies following the process described [here](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md/#adding-new-unconventional-dependencies)

### New Features

* [ ] Have you added the new feature to an [integration test](https://github.com/aws/aws-cdk/blob/main/INTEGRATION_TESTS.md)?
	* [ ] Did you use `yarn integ` to deploy the infrastructure and generate the snapshot (i.e. `yarn integ` without `--dry-run`)?

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: mrgrain

.gitignore

@@ -34,6 +34,7 @@ cdk.context.json
 .cdk.staging/
 cdk.out/
 *.tabl.json
+cdk-integ.out.*/
 
 # Yarn error log
 yarn-error.log

packages/@aws-cdk/aws-lambda/test/cdk-integ.out/cdk.out

@@ -27,7 +27,11 @@ junit.xml
 # Ignore this symlink, we recreate it at test time
 test/test-archive-follow/data/linked
 
+# These files are needed for unit tests
+!test/test-data/cdk-integ.out*/
+
 !**/*.snapshot/**/asset.*/*.js
 !**/*.snapshot/**/asset.*/*.d.ts
 
 !**/*.snapshot/**/asset.*/**
+