[services] Tunnelbroker - Function to put message items to the database by batch

Summary:
This diff introduces the function to put messages to the database by a batch using the innerBatchWriteItem function from D4373.

Linear task: ENG-1301

Test Plan: Run test from D4377

Reviewers: karol, tomek

Reviewed By: karol, tomek

Subscribers: ashoat, tomek, adrian, atul, karol, abosh

Differential Revision: https://phab.comm.dev/D4378