fix(pipelines): prevent self-mutation on asset updates (aws#9183)

Currently, changes to the asset hashes of content results in changes to the
definitions of the pipeline, causing the self-mutate state to trigger. This can
cause infinite loops for systems where build artifacts change on each build.

The cause for this looping is that the asset hash was embedded as the pipeline
action name. By replacing the asset hash with a simple asset counter (already
used for the action CloudFormation id), the pipeline definition should remain
stable on asset changes.

_Testing:_ Due to the pipeline executing the current version of CDK within the
pipeline, it's impossible to actual verify that this corrects the issue. To
test + verify, created a sample app where the asset hash changed on each build.
Then ran subsequent 'cdk synth' commands and diff'ed the output. Prior to this
change, there were numerous changes related to the asset hash in the pipeline
stack. After, only the buildspec of the CodeBuild project that referenced the
hash changed. This does not change the definition of the CodePipeline itself.

fixes aws#9080

----

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

packages/@aws-cdk/pipelines/lib/pipeline.ts

@@ -279,7 +279,7 @@ class AssetPublishing extends Construct {
       const id = command.assetType === AssetType.FILE ? `FileAsset${this._fileAssetCtr++}` : `DockerAsset${this._dockerAssetCtr++}`;
 
       action = this.publishers[command.assetId] = new PublishAssetsAction(this, id, {
-        actionName: command.assetId,
+        actionName: id,
         cloudAssemblyInput: this.props.cloudAssemblyInput,
         cdkCliVersion: this.props.cdkCliVersion,
         assetType: command.assetType,

packages/@aws-cdk/pipelines/test/pipeline-assets.test.ts

@@ -82,7 +82,7 @@ test('assets are also published when using the lower-level addStackArtifactDeplo
       Name: 'Assets',
       Actions: [
         objectLike({
-          Name: FILE_ASSET_SOURCE_HASH,
+          Name: 'FileAsset1',
           RunOrder: 1,
         }),
       ],