RPC server: added PID and tag to resto logs

What

Adding PID and [resto] tag to Resto logs.

Why

Resto is running in several processes in Tezos: RPC server and External RPC process. We need to distinguish their outputs. Added [resto] tag to simply finding resto logs.

How

Added pid and tag to the Logging module provided to Resto on launch.

Manually testing the MR

TEZOS_LOG="*->debug" ./src/bin_node/octez-sandboxed-node.sh 1 --connections 0
eval $(./src/bin_client/octez-init-sandboxed-client.sh 1)
TEZOS_LOG="*->debug"  octez-activate-alpha

Logs before:

Jun 04 16:47:59.158: connection closed 18
Jun 04 16:47:59.158: connection closed 12
Jun 04 16:47:59.158: streamed connection closed 12

Logs after:

Jun 04 16:50:28.481: [pid:16129][resto] connection closed 18
Jun 04 16:50:28.482: [pid:16070][resto] connection closed 12
Jun 04 16:50:28.482: [pid:16070][resto] streamed connection closed 12

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR