Add provider filtering and matching endpoint to Synapse API

### Feature Request: Provider Filtering/Matching Endpoint for Synapse

**Background**
Related to [issue FilOzone/filecoin-services#119](https://github.com/FilOzone/filecoin-services/issues/119): transitioning to a unified service provider registry. To improve discoverability for clients/service creators, Synapse should offer an API endpoint for filtering and matching service providers.

**Proposal**
Introduce an endpoint (e.g., `synapse.providerFiltering` or `synapse.matchProviders`) that allows users (client, service creator, dapp buidler, onramps..) to easily search and filter the service provider pool based on product properties and location.

**Initial Filtering Criteria:**
- Product type
- Location
- Product properties (e.g., sector size, piece size, publisher presence)

**Expected Output:**
- Returns a list/JSON of matched service providers, including their unique ID, metadata, and relevant service product.
- No ranking/sorting to start with; could consider randomizing the ordering but also okay to leave it to the SDK user?

**Reputation/Scoring Integration (Future Expansion Consideration):**
-When there exists scoring/reputation services, we can consider adding reputation or scoring metrics to provider matching and filtering/sorting results.

No files, tests, or existing entry points are named. Start by locating the Synapse SDK's provider and API entry points, then clarify the provider registry and filtering contract; done means a defined endpoint that filters by product type, location, and product properties and returns matched providers with IDs, metadata, and relevant products.

Written by the indexing model from the issue text.