Rename storageProvider type from durabletask-scheduler to azureManaged

[Copilot]

Unifies the storageProvider.type value across all languages to azureManaged, replacing the previously non-.NET-specific durabletask-scheduler identifier.

Changes

• host.json samples — updated storageProvider.type in Java, JavaScript, and .NET (DistributedTracing) samples
• Skill documentation — updated all code examples in SKILL.md and references/backends.md "What to Replace With" sections for Python/JS/Java migration paths
• Doc text — removed language distinguishing .NET vs non-.NET type values; both now use azureManaged

// Before
"storageProvider": {
  "type": "durabletask-scheduler",
  "connectionStringName": "DURABLE_TASK_SCHEDULER_CONNECTION_STRING"
}

// After
"storageProvider": {
  "type": "azureManaged",
  "connectionStringName": "DURABLE_TASK_SCHEDULER_CONNECTION_STRING"
}