☂️ Upgrade the etcd from `v3.5.27` to `v3.6.x`

[ishan16696]

/area storage
/kind enhancement

What would you like to be added:
Upgrade etcd from v3.5.27 to v3.6.x

Motivation (Why is this needed?):

1. Upstream etcd is planning to cut the release of etcd v3.7 after that they might end the support for v3.5.x may be in a year or so.
2. Moreover, other important feature and fixes like this Fix race between read index and leader change etcd-io/etcd#21375 and etcdutl: use map to count unique user keys in snapshot status etcd-io/etcd#19344 etc.

Breaking changes to account for:

• v2 store is gone entirely.
• etcdctl snapshot/defrag commands moved to etcdutl .

The upgrade will be completed stepwise:

• Upgrade to v3.6.x in etcd-backup-restore
• Upgrade to v3.6.x in etcd-wrapper
• Upgrade to v3.6.x in etcd-druid

Approach/Hint to implement solution (optional):
We need to determine the exact stable patch version of v3.6.x suitable for production. Please also go through such blog from upstream to read about already known issues: https://etcd.io/blog/2025/zombie_members_upgrade/