disable entity filter when application_signals is disabled

[movence]

Issue

When customers use a custom config without Application Signals, FluentBit's Enable_Entity flag causes connection errors to cloudwatch-agent:4311 (entity endpoint).

[warn] [net] getaddrinfo(host='cloudwatch-agent.amazon-cloudwatch', err=-2): Name or service not known
[error] [filter:kubernetes:kubernetes.1] no upstream connections available to cloudwatch-agent.amazon-cloudwatch:4311

Description of changes:

Added logic to conditionally set Enable_Entity based on agent config:

• _helpers.tpl: Added fluent-bit.hasAppSignals helper to detect if application_signals is in agent config
• _helpers.tpl: Added fluent-bit.set-entity-flag helper to set the flag accordingly
• fluent-bit-configmap.yaml: Applied the helper when rendering config

Tested using helm template test

> TEST 1: Default agent config (has application_signals)

Agent config:
{
  "logs": {
    "metrics_collected": {
      "kubernetes": { "enhanced_container_insights": true },
      "application_signals": { }
    }
  },
  "traces": {
    "traces_collected": {
      "application_signals": { }
    }
  }
}

Enable_Entity: true
Use_Pod_Association: On
add_entity: true

> TEST 2: Custom agent config (NO application_signals)

Agent config override:
agent.config.logs.metrics_collected.kubernetes.enhanced_container_insights=true
(no application_signals key)

Enable_Entity: false
Use_Pod_Association: Off
add_entity: false

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