Allow dependsOn on existing resources

[jeskew]

Is your feature request related to a problem? Please describe.
In the ARM engine, the workaround for issues like #7402 is to declare explicit dependencies (via the dependsOn property) in the body of an existing resource declaration that corresponds to the resource on which the list* function will be called. Bicep currently disallows the dependsOn property in existing resources because such a declaration is nonsensical in non-symbolic name templates.

Describe the solution you'd like
Bicep should allow the use of dependsOn in existing resources, and the presence of any existing resources with explicit dependencies should result in Bicep using symbolic name compilation.