[Feature Request]: Export schema.sql or data.sql

### Feature Description

Support to export schema.sql, data.sql or both from a selected database

### Problem and Motivation

Microsoft sql server management studio already have implemented it, good for windows users, but linux users only have dacpac or bacpac options

### Related Area

- [ ] Connection dialog (SQL Server | Azure browse/Fabric browse)
- [ ] Query editor
- [ ] Query results panel
- [ ] Object Explorer
- [ ] GitHub Copilot integration
- [ ] Preview/Edit data
- [ ] Table Designer
- [ ] Schema Designer
- [ ] Schema Compare
- [ ] Local SQL Server Container provisioning
- [ ] SQL database in Fabric provisioning
- [x] DACPAC/BACPAC export/import
- [ ] SQL Database projects
- [ ] Query Plan Visualizer
- [ ] Other (please describe below)

### If you selected "Other", please describe the area

_No response_

### Confirmation

- [x] I have searched existing feature requests and couldn't find a match
- [x] I want to help implement this feature

Start by locating the existing DACPAC/BACPAC export and import entry points in the extension, then review how a selected database is handled. Done means users can choose schema.sql, data.sql, or both when exporting a selected database, with the behavior validated for the supported SQL Server scenarios.

Written by the indexing model from the issue text.