feat: add the Gemini Data Analytics (GDA) integration for DB NL2SQL conversion to Toolbox (#2181)

## Description

This PR is to add the Gemini Data Analytics (GDA) integration for DB
NL2SQL conversion to Toolbox. It allows the user to convert a natural
language query to SQL statement based on their database instance. See
the doc section for details.

## PR Checklist

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- [x] Make sure you reviewed

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- [x] Ensure the tests and linter pass
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🛠️ Fixes #2180

---------

Co-authored-by: Yuan Teoh <45984206+Yuan325@users.noreply.github.com>

cmd/root.go

@@ -73,6 +73,7 @@ import (
 	_ "github.com/googleapis/genai-toolbox/internal/tools/clickhouse/clickhouselistdatabases"
 	_ "github.com/googleapis/genai-toolbox/internal/tools/clickhouse/clickhouselisttables"
 	_ "github.com/googleapis/genai-toolbox/internal/tools/clickhouse/clickhousesql"
+	_ "github.com/googleapis/genai-toolbox/internal/tools/cloudgda"
 	_ "github.com/googleapis/genai-toolbox/internal/tools/cloudhealthcare/cloudhealthcarefhirfetchpage"
 	_ "github.com/googleapis/genai-toolbox/internal/tools/cloudhealthcare/cloudhealthcarefhirpatienteverything"
 	_ "github.com/googleapis/genai-toolbox/internal/tools/cloudhealthcare/cloudhealthcarefhirpatientsearch"