Add pending transactions from the mempool to the transaction history

[MuesliSwapTeam]

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This is a first part of a line of contributions based on the Catalyst Proposal Open Transaction Chaining tooling to speed up Cardano dApps - By MuesliSwap.

This PR introduces a feature to show pending transactions in the list of historic transactions. Concretely, transactions present in the Blockfrost mempool (this includes all transactions submitted through Blockfrost, such as those submitted through Nami Wallet) will be shown on top of the list of historic transactions and marked as "pending". This greatly enhances user feedback, as users will almost immediately see transactions popping up after submission and do not have to wait for inclusion on the blockchain. As soon as the transaction is confirmed on the blockchain, it will be shown as usual.

See below for a short demonstration of the feature:

https://github.com/input-output-hk/nami/assets/91151317/bd3fa1b4-082d-4e50-b76c-6c1c039c586c