feat(pebble): support pinning FormatMajorVersion

[gammazero]

• Configure latest pebble database format at init
• Do not automatically ratchet database format if set in config
• Daemon message about new available pebble format
• expose and document formatMajorVersion
• add warning to users running badger, nudging them to switch to flatfs or pebble

Closes #10347

[lidel]

Lgtm, feels like a sensible compromise, and low risk since pebble is still opt-in.

@gammazero there is a failing sharness I assume it needs landing #10788 first?

Example

ipfs init --profile=pebbleds creates config with explicit formatMajorVersion

  "Datastore": {                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
    "Spec": {                                                                                                                                                                                                                                                                
      "child": {                                                                                                                                                                                                                                                             
        "formatMajorVersion": 19,                                                                                                                                                                                                                                            
        "path": "pebbleds",                                                                                                                                                                                                                                                  
        "type": "pebbleds"                                                                                                                                                                                                                                                   
      },                                                                                                                                                                                                                                                                     
      "prefix": "pebble.datastore",                                                                                                                                                                                                                                          
      "type": "measure"                                                                                                                                                                                                                                                      
    },                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
  },

manually setting 18 (to simulate future pebble format update scenario) triggers below warning:

> ipfs daemon
Initializing daemon...
Kubo version: 0.35.0-dev-32612eb7a
Repo version: 16
System version: amd64/linux
Golang version: go1.24.2
⚠️ A newer pebble db format is available.
  To upgrade, set the following in the pebble datastore config:
    "formatMajorVersion": 19
PeerID: 12D3KooWSDFGEkyKaUhUjJVFK6JKhrp1NRhvwx2ffjQrm36fPokj
Swarm listening on 127.0.0.1:4001 (TCP+UDP)
Swarm listening on [::1]:4001 (TCP+UDP)
Run 'ipfs id' to inspect announced and discovered multiaddrs of this node.
RPC API server listening on /ip4/127.0.0.1/tcp/5001
WebUI: http://127.0.0.1:5001/webui
Gateway server listening on /ip4/127.0.0.1/tcp/8080
Daemon is ready

cc @hsanjuan for visibility on how Kubo deal with this