feat!: update configuration file v2 (#2369)

This PR introduces a significant update to the Toolbox configuration
file format, which is one of the primary **breaking changes** required
for the implementation of the Advanced Control Plane.

# Summary of Changes
The configuration schema has been updated to enforce resource isolation
and facilitate atomic, incremental updates.
* Resource Isolation: Resource definitions are now separated into
individual blocks, using a distinct structure for each resource type
(Source, Tool, Toolset, etc.). This improves readability, management,
and auditing of configuration files.
* Field Name Modification: Internal field names have been modified to
align with declarative methodologies. Specifically, the configuration
now separates kind (general resource type, e.g., Source) from type
(specific implementation, e.g., Postgres).

# User Impact
Existing tools.yaml configuration files are now in an outdated format.
Users must eventually update their files to the new YAML format.

# Mitigation & Compatibility
Backward compatibility is maintained during this transition to ensure no
immediate user action is required for existing files.
* Immediate Backward Compatibility: The source code includes a
pre-processing layer that automatically detects outdated configuration
files (v1 format) and converts them to the new v2 format under the hood.
* [COMING SOON] Migration Support: The new toolbox migrate subcommand
will be introduced to allow users to automatically convert their old
configuration files to the latest format.

# Example
Example for config file v2:
```
kind: sources
name: my-pg-instance
type: cloud-sql-postgres
project: my-project
region: my-region
instance: my-instance
database: my_db
user: my_user
password: my_pass
---
kind: authServices
name: my-google-auth
type: google
clientId: testing-id
---
kind: tools
name: example_tool
type: postgres-sql
source: my-pg-instance
description: some description
statement: SELECT * FROM SQL_STATEMENT;
parameters:
- name: country
  type: string
  description: some description
---
kind: tools
name: example_tool_2
type: postgres-sql
source: my-pg-instance
description: returning the number one
statement: SELECT 1;
---
kind: toolsets
name: example_toolset
tools:
- example_tool
```

---------

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
Co-authored-by: Averi Kitsch <akitsch@google.com>

docs/en/resources/tools/cloudsql/cloudsqlmssqlcreateinstance.md

@@ -9,17 +9,17 @@ The `cloud-sql-mssql-create-instance` tool creates a Cloud SQL for SQL Server
 instance using the Cloud SQL Admin API.
 
 {{< notice info dd>}}
-This tool uses a `source` of kind `cloud-sql-admin`.
+This tool uses a `source` of type `cloud-sql-admin`.
 {{< /notice >}}
 
 ## Example
 
 ```yaml
-tools:
-  create-sql-instance:
-    kind: cloud-sql-mssql-create-instance
-    source: cloud-sql-admin-source
-    description: "Creates a SQL Server instance using `Production` and `Development` presets. For the `Development` template, it chooses a 2 vCPU, 8 GiB RAM (`db-custom-2-8192`) configuration with Non-HA/zonal availability. For the `Production` template, it chooses a 4 vCPU, 26 GiB RAM (`db-custom-4-26624`) configuration with HA/regional availability. The Enterprise edition is used in both cases. The default database version is `SQLSERVER_2022_STANDARD`. The agent should ask the user if they want to use a different version."
+kind: tools
+name: create-sql-instance
+type: cloud-sql-mssql-create-instance
+source: cloud-sql-admin-source
+description: "Creates a SQL Server instance using `Production` and `Development` presets. For the `Development` template, it chooses a 2 vCPU, 8 GiB RAM (`db-custom-2-8192`) configuration with Non-HA/zonal availability. For the `Production` template, it chooses a 4 vCPU, 26 GiB RAM (`db-custom-4-26624`) configuration with HA/regional availability. The Enterprise edition is used in both cases. The default database version is `SQLSERVER_2022_STANDARD`. The agent should ask the user if they want to use a different version."
 ```
 
 ## Reference
@@ -28,7 +28,7 @@ tools:
 
 | **field**   | **type** | **required** | **description**                                  |
 | ----------- | :------: | :----------: | ------------------------------------------------ |
-| kind        |  string  |     true     | Must be "cloud-sql-mssql-create-instance".       |
+| type        |  string  |     true     | Must be "cloud-sql-mssql-create-instance".       |
 | source      |  string  |     true     | The name of the `cloud-sql-admin` source to use. |
 | description |  string  |    false     | A description of the tool.                       |