feat: add metadata in MCP Manifest for Toolbox auth (#1395)

Add `_meta` for `tools/list` method in MCP Toolbox.

If there are authorized invocation, the following will be return in
`_meta`:
```
{
    "name":"my-tool-name",
    "description":"my tool description",
     "inputSchema":{
        "type":"object",
         "properties":{
             "user_id":{"type":"string","description":"user's name from google login"}
         },
         "required":["user_id"]
     },
     "_meta":{
         "toolbox/authParam":{"user_id":["my_auth"]}
     }
}
```

If there are authenticated parameter, the following will be return in
`_meta`:
```
{
    "name":"my-tool-name",
    "description":"my tool description",
    "inputSchema":{
        "type":"object",
        "properties":{
            "sql":{"type":"string","description":"The sql to execute."}
        },
        "required":["sql"]
    },
    "_meta":{
        "toolbox/authInvoke":["my_auth"]
    }
}
```

If there are no authorized invocation or authenticated prameter, the
`_meta` field will be omitted.


With this feature, the following were updated in the source code: 
* In each `func(p CommonParameter) McpManifest()`, we will return a
`[]string` for the list of authenticated parameters. This is similar to
how Manifest() return the list of authNames in non-MCP Toolbox's
manifest.
* The `func(ps Parameters) McpManifest()` will return a
`map[string][]string` that with key as param's name, and value as the
param's auth.
* Added a new function `GetMcpManifest()` in `tools.go`. This function
will consctruct the McpManifest, and add the `Metadata` field.
* Associated tests were added or updated.

internal/tools/cloudsql/cloudsqlcreateusers/cloudsqlcreateusers.go

@@ -78,18 +78,11 @@ func (cfg Config) Initialize(srcs map[string]sources.Source) (tools.Tool, error)
 	}
 	paramManifest := allParameters.Manifest()
 
-	inputSchema := allParameters.McpManifest()
-
 	description := cfg.Description
 	if description == "" {
 		description = "Creates a new user in a Cloud SQL instance. Both built-in and IAM users are supported. IAM users require an email account as the user name. IAM is the more secure and recommended way to manage users. The agent should always ask the user what type of user they want to create. For more information, see https://cloud.google.com/sql/docs/postgres/add-manage-iam-users"
 	}
-
-	mcpManifest := tools.McpManifest{
-		Name:        cfg.Name,
-		Description: description,
-		InputSchema: inputSchema,
-	}
+	mcpManifest := tools.GetMcpManifest(cfg.Name, description, cfg.AuthRequired, allParameters)
 
 	return Tool{
 		Name:         cfg.Name,