chore(cli-integ): make the version of cli-lib-alpha switchable (#33450)

The `@aws-cdk/cli-lib-alpha` package is vended as an alpha package in the old pipeline.

That means its version number is `2.178.1-alpha.0` for a real release, or `2.178.1-alpha.999` for a release candidate, with the version component matching the framework version.

In the new pipeline, we'll have to decouple from the framework version to the CLI version anyway, and I don't want to have to rebuild this version mangling logic in projen. Instead, we'll just always take the CLI version and append `-alpha.0`. That may mean we'll end up with a release candidate version of `-rc.0-alpha.0`, which looks weird but I don't think will break anything.

----

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

Author: rix0rrr

packages/@aws-cdk-testing/cli-integ/lib/with-cli-lib.ts

@@ -37,9 +37,16 @@ export function withCliLibIntegrationCdkApp<A extends TestContext & AwsContext &
       }
 
       const alphaInstallationVersion = fixture.packages.requestedAlphaVersion();
+
+      // cli-lib-alpha has a magic alpha version in the old release pipeline,
+      // but will just mirror the CLI version in the new pipeline.
+      const cliLibVersion = process.env.CLI_LIB_VERSION_MIRRORS_CLI
+        ? `${fixture.packages.requestedCliVersion()}-alpha.0`
+        : alphaInstallationVersion;
+
       await installNpmPackages(fixture, {
         'aws-cdk-lib': installationVersion,
-        '@aws-cdk/cli-lib-alpha': alphaInstallationVersion,
+        '@aws-cdk/cli-lib-alpha': cliLibVersion,
         '@aws-cdk/aws-lambda-go-alpha': alphaInstallationVersion,
         '@aws-cdk/aws-lambda-python-alpha': alphaInstallationVersion,
         'constructs': '^10',