Add Alchemy as a new RPC provider (stellar#2321)

* Add Alchemy as a new RPC provider

* Update Exaion and Alchemy archive status

Updated the Exaion and Alchemy entries to indicate they no longer provide dedicated nodes.

* Apply suggestion from @Copilot

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update Exaion support status in providers table

* Fix Alchemy link to point to dashboard with referral

Updated Alchemy link to direct to the dashboard with referral parameters.

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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: 2 people

docs/data/apis/rpc/providers.mdx

@@ -21,7 +21,8 @@ These providers allow access to the Futurenet, Testnet and Mainnet network.
 | [OnFinality\*](https://onfinality.io/networks/stellar) | ❌ | ❌ | ✅ | ✅ | ✅ |
 | [Lightsail Network - Quasar\*](https://quasar.lightsail.network/) | ❌ | ❌ | ✅ | ❌ | ✅ |
 | [Uniblock](https://www.uniblock.dev/) | ❌ | ✅ | ✅ | ❌ | ❌ |
-| [Exaion](https://crypto.exaion.com) | ❌ | ❌ | ✅ | ✅ |
+| [Exaion](https://crypto.exaion.com) | ❌ | ❌ | ✅ | ✅ | ✅ |
+| [Alchemy](https://dashboard.alchemy.com/?utm_source=chain_partner&utm_medium=referral&utm_campaign=stellar) | ❌ | ✅ | ✅ | ✅ | ❌ |
 
 \*_RPC Archive is a new option for those looking to retrieve full ledger history. Currently only the [getLedgers](./api-reference/methods/getLedgers.mdx) RPC method supports this feature. You can choose one of the providers above, or create your own getLedgers archive by following [these steps](./admin-guide/data-lake-integration.mdx)._