Add agent engine BYOC support (#3885)

* feat(agent-engine): add support for container and custom image specs

- Add container_config to deployment_files.
- Add image_spec with build_args to source_config.
- Make agent_framework optional and document supported values.
- Implement dynamic specs for container and source deployments.
- Add examples and automated tests for new deployment types.

* chore: update Google provider version to 7.28.0 across modules

Mechanical update of versions.tf and versions.tofu files using tools/versions.py.

* feat(agent-engine): refactor for container deployments and API alignment

- Group deployment settings under 'deployment_config' (renamed from 'deployment_files').
- Support container-based deployments via 'container_config' and 'image_spec'.
- Refactor 'source_files_config' (renamed from 'source_config') to include mutually exclusive 'python_spec' and 'image_spec'.
- Support 'developer_connect_config' as a source code type.
- Group engine settings (framework, env, secrets) under 'agent_engine_config'.
- Add support for 'memory_bank_config' persistent memory.
- Overhaul reasoning engine resources with dynamic blocks to match provider schema.
- Update all documentation examples, add TOC, and refresh test inventories.

* Update dynamic python_spec block and related example yamls

* Ignore changes setting for developer_connect_source under lifecycle management

* fixing review comments for `try` and default path for `source_path`

---------

Co-authored-by: Hemanand <hemr@google.com>
Co-authored-by: Julio Castillo <jccb@google.com>

modules/net-lb-int/versions.tf

@@ -19,11 +19,11 @@ terraform {
   required_providers {
     google = {
       source  = "hashicorp/google"
-      version = ">= 7.27.0, < 8.0.0" # tftest
+      version = ">= 7.28.0, < 8.0.0" # tftest
     }
     google-beta = {
       source  = "hashicorp/google-beta"
-      version = ">= 7.27.0, < 8.0.0" # tftest
+      version = ">= 7.28.0, < 8.0.0" # tftest
     }
   }
   provider_meta "google" {

modules/net-lb-int/versions.tofu

@@ -19,11 +19,11 @@ terraform {
   required_providers {
     google = {
       source  = "hashicorp/google"
-      version = ">= 7.27.0, < 8.0.0" # tftest
+      version = ">= 7.28.0, < 8.0.0" # tftest
     }
     google-beta = {
       source  = "hashicorp/google-beta"
-      version = ">= 7.27.0, < 8.0.0" # tftest
+      version = ">= 7.28.0, < 8.0.0" # tftest
     }
   }
   provider_meta "google" {