Why this should be merged

Moves atomic gossip files and handlers to atomic pkg
Removes legacy non-used gossip handler

How this works

This pull request includes several changes to the peer/network.go and plugin/evm files, primarily focused on removing the gossip handler functionality and refactoring the atomic transaction handling. The most important changes include removing the gossip handler, updating the network struct and its methods, and adding new functionality for atomic transactions.

Removal of Gossip Handler:

• peer/network.go: Removed the SetGossipHandler method and the gossipHandler field from the network struct. Updated related methods to remove references to the gossip handler. [1] [2] [3] [4] [5]

Refactoring of Atomic Transactions:

• plugin/evm/atomic/gossip.go: Added new file to handle gossip-related functionality for atomic transactions, including GossipAtomicTxMarshaller and GossipAtomicTx types.
• plugin/evm/atomic/mempool.go: Renamed and refactored the mempool handling for atomic transactions, including updating import paths and changing types from atomic.Tx to Tx. [1] [2] [3] [4]

Test Updates:

• peer/network_test.go: Updated tests to reflect the removal of the gossip handler and the introduction of atomic transaction handling, including changes to the sync/atomic import and various test functions. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]

Minor Changes:

• plugin/evm/admin.go: Updated the GetVMConfig method to use client.ConfigReply instead of a local ConfigReply type.

These changes improve the codebase by removing unused functionality and refactoring existing code to better handle atomic transactions and their related operations.

How this was tested

UT/E2E tests should cover this.

Need to be documented?

No

Need to update RELEASES.md?

Yes