Add WithExplicitStart to conditionally not start some resources

[JamesNK]

Description

WithExplicitStart adds a annotation that instructs DCP not to start the resource. Resources with this attribute have the NotStarted state. The dashboard knows about this state and gives it an appropriate icon and enables the start command.

Fixes #5879

TODO:

• Tests

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
    • Is this introducing a breaking change?
      • Yes
        • Link to aspire-docs issue (please use this breaking-change template):
      • No
        • Link to aspire-docs issue (please use this doc-idea template):
  • No

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src/Aspire.Hosting/ResourceBuilderExtensions.cs:757

• The new method WithExplicitStart should be covered by tests to ensure its functionality.

public static IResourceBuilder<T> WithExplicitStart<T>(this IResourceBuilder<T> builder) where T : IResource