chore: prepare release 2.1.0

[github-actions]

This PR was created automatically. Merging it will finalize the changelog for 2.1.0

Features

• The RHP4 port can now be set using the -rhp4 flag.
• Added Prometheus support to [GET] /syncer/peers

Add endpoints for querying V2 contracts

Adds two new endpoints for querying V2 contracts

[GET] /v2/contracts/:id

Returns a single V2 contract by its ID

[POST] /v2/contracts

Queries a list of contracts with optional filtering

Example request body

{
  "statuses": [],
  "contractIDs": [],
  "renewedFrom": [],
  "renewedTo": [],
  "renterKey": [],
  "minNegotiationHeight": 0,
  "maxNegotiationHeight": 0,
  "minExpirationHeight": 0,
  "maxExpirationHeight": 0,
  "limit": 0,
  "offset": 0,
  "sortField": "",
  "sortDesc": false
}

Add QUIC support

Adds QUIC transport support in RHP4, enabling Sia network access through web browsers. This update also simplifies cross-language development by using a standard protocol.

Add support for RPCReplenish

Adds support RPCReplenish, simplifying management for renters with a large number of accounts.

Fixes

• Combine update and select query when pruning sectors to force usage of exclusive database transaction
• Fixed broken API client consensus methods
• Fix JSON field names for V2Contract type
• Fixed an issue with v2 contract sector roots not being reloaded
• Reduced migration time for large mostly empty volumes
• Update module path to go.sia.tech/hostd/v2