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Existing tools.yaml configuration files are now in an outdated format.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pre-processing layer that automatically detects outdated configuration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>

internal/sources/cloudsqlpg/cloud_sql_pg.go

@@ -28,14 +28,14 @@ import (
 	"go.opentelemetry.io/otel/trace"
 )
 
-const SourceKind string = "cloud-sql-postgres"
+const SourceType string = "cloud-sql-postgres"
 
 // validate interface
 var _ sources.SourceConfig = Config{}
 
 func init() {
-	if !sources.Register(SourceKind, newConfig) {
-		panic(fmt.Sprintf("source kind %q already registered", SourceKind))
+	if !sources.Register(SourceType, newConfig) {
+		panic(fmt.Sprintf("source type %q already registered", SourceType))
 	}
 }
 
@@ -49,7 +49,7 @@ func newConfig(ctx context.Context, name string, decoder *yaml.Decoder) (sources
 
 type Config struct {
 	Name     string         `yaml:"name" validate:"required"`
-	Kind     string         `yaml:"kind" validate:"required"`
+	Type     string         `yaml:"type" validate:"required"`
 	Project  string         `yaml:"project" validate:"required"`
 	Region   string         `yaml:"region" validate:"required"`
 	Instance string         `yaml:"instance" validate:"required"`
@@ -59,8 +59,8 @@ type Config struct {
 	Password string         `yaml:"password"`
 }
 
-func (r Config) SourceConfigKind() string {
-	return SourceKind
+func (r Config) SourceConfigType() string {
+	return SourceType
 }
 
 func (r Config) Initialize(ctx context.Context, tracer trace.Tracer) (sources.Source, error) {
@@ -88,8 +88,8 @@ type Source struct {
 	Pool *pgxpool.Pool
 }
 
-func (s *Source) SourceKind() string {
-	return SourceKind
+func (s *Source) SourceType() string {
+	return SourceType
 }
 
 func (s *Source) ToConfig() sources.SourceConfig {
@@ -162,7 +162,7 @@ func getConnectionConfig(ctx context.Context, user, pass, dbname string) (string
 
 func initCloudSQLPgConnectionPool(ctx context.Context, tracer trace.Tracer, name, project, region, instance, ipType, user, pass, dbname string) (*pgxpool.Pool, error) {
 	//nolint:all // Reassigned ctx
-	ctx, span := sources.InitConnectionSpan(ctx, tracer, SourceKind, name)
+	ctx, span := sources.InitConnectionSpan(ctx, tracer, SourceType, name)
 	defer span.End()
 
 	// Configure the driver to connect to the database