feat: Nominatim OpenStreetMap search tool

[chazzhou]

Description

This pull request introduces a new Nominatim OpenStreetMap search tool to Dify. The tool allows users to perform geocoding, reverse geocoding, and OSM object lookup using the Nominatim API. It supports both the public Nominatim service and self-hosted instances.

Key features:

• Geocoding: Search for locations by address or place name
• Reverse geocoding: Convert coordinates to addresses
• OSM object lookup: Retrieve information about OSM objects by their IDs
• Configurable base URL for self-hosted instances

This feature enhances Dify's capabilities in location-based applications.

Type of Change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• Tested geocoding with various addresses and place names
• Tested reverse geocoding with different coordinate pairs
• Tested OSM object lookup with node, way, and relation IDs

Suggested Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

[crazywoola]

LGTM