[v23.2.x] Added size bytes background flush to Raft

[vbotbuildovich]

Backport #13586 to branch v23.2.x. Note that this issue was created as a placeholder, since the original PR's commit(s) could not be automatically cherry-picked.
Here are the commands to execute:

git checkout v23.2.x
git checkout -b vbotbuildovich/backport-13586-v23.2.x-751
git cherry-pick -x 67064fcf75a856762e8216c25839005784df75a4 de49f0c36617f33de76e92a09497e7c653d7b4dc f9c2ac22dd94baec0614b6e55ff18e3fefdb40c8 d8527018bd3486a2d5d91322be96b23b868d6f53 4688bc944fbf4d509b18f47464cd73d5123286d0 0cc8f55fac4d4068f7cd843be33ce1668d06b329 1d6e8cce19d58f902bb3d5bce54b038b5649b67e 0a7355187f6f28ab73331ef337e9f4d573d2c29e ce1ff990aea244e9135facc4f956e0ab3de8f9f7

git push origin vbotbuildovich/backport-13586-v23.2.x-751
gh pr create \
  --title "[v23.2.x] Added size bytes background flush to Raft" \
  --base "v23.2.x" \
  --label "kind/backport" \
  --head "vbotbuildovich/backport-13586-v23.2.x-751" \
  --draft \
  --repo "redpanda-data/redpanda" \
  --reviewer "bharathv,rystsov,StephanDollberg" \
  --milestone "v23.2.x-next" \
  --body "Backport of PR https://github.com/redpanda-data/redpanda/pull/13586 "