Chore: deprecate unused D1 commands/options for wrangler v4

[rozenmd]

This will be a breaking change, so will need to go into wrangler v4.

In short, we need to:

• remove any alpha-specific code paths from the d1 commands
• remove --batch-size from wrangler d1 execute (long deprecated and not needed)
• remove --batch-size from wrangler d1 migrations (long deprecated and not needed)
• remove wrangler d1 backups commands (unsupported by production DBs, alpha dbs are deprecated)

[penalosa]

This has been merged to the v4 RC