Add WellKnownPipelineTags to default pipeline steps and rename GetSteps to GetStepsByTag

[Copilot]

Description

Default pipeline steps in DistributedApplicationPipeline were not tagged, preventing them from being queried by tag in pipeline configuration callbacks. This made it difficult to create dependencies on groups of default steps (e.g., "run after all build steps complete").

Changes:

• Tagged Deploy and DeployPrereq with DeployCompute and ProvisionInfrastructure respectively
• Tagged Build and BuildPrereq with BuildCompute
• Tagged Publish and PublishPrereq with PushContainerImage
• Left Diagnostics step untagged (debugging/troubleshooting step, not part of deployment workflow)
• Added test to verify tag assignments
• Renamed GetSteps(string tag) to GetStepsByTag(string tag) for clarity when multiple overloads exist

Usage:

pipeline.AddPipelineConfiguration((context) =>
{
    // Can now query default steps by tag
    var buildSteps = context.GetStepsByTag(WellKnownPipelineTags.BuildCompute);
    var provisionSteps = context.GetStepsByTag(WellKnownPipelineTags.ProvisionInfrastructure);
    
    // Create dependencies on groups of steps
    myStep.DependsOn(buildSteps);
});

Aligns default steps with tagging pattern already used by resource-specific steps (e.g., ProjectResource, AzureBicepResource).

Checklist

• Is this feature complete?
  • Yes. Ready to ship.
  • No. Follow-up changes expected.
• Are you including unit tests for the changes and scenario tests if relevant?
  • Yes
  • No
• Did you add public API?
  • Yes
    • If yes, did you have an API Review for it?
      • Yes
      • No
    • Did you add <remarks /> and <code /> elements on your triple slash comments?
      • Yes
      • No
  • No
• Does the change make any security assumptions or guarantees?
  • Yes
    • If yes, have you done a threat model and had a security review?
      • Yes
      • No
  • No
• Does the change require an update in our Aspire docs?
  • Yes
    • Link to aspire-docs issue (consider using one of the following templates):
      • New (or update) doc-idea template
      • New breaking-change template
      • New diagnostic template
  • No

Original prompt

Add tags to all the steps that are registered by default in the DistributedApplicationPipeline and have a WellKnownPipelineTag.

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[davidfowl]

@copilot Lets rename this to GetStepsByTag since it's a string overload.

[Copilot]

@copilot Lets rename this to GetStepsByTag since it's a string overload.

Done in ddc23a1. Renamed GetSteps(string tag) to GetStepsByTag(string tag) and updated all test usages.