[wrangler] Add --json flag to r2 bucket info command

[Akshit222]

What

Adds a --json flag to the wrangler r2 bucket info command, returning the bucket info in clean JSON format.

Why

Fixes #9433 — The current output is not machine-readable. Adding this makes the output usable in scripts and consistent with D1 commands that already support --json.

How

• Adds a --json flag to r2 bucket info
• Omits verbose output when --json is passed
• Adds a unit test verifying valid JSON output

Test Plan

• ✅ pnpm exec vitest run packages/wrangler/src/__tests__/r2/bucket.test.ts passed
• ✅ Manual output verified

Notes

Currently, the banner line (⛅ wrangler 4.18.0) still appears even when using --json.
I left it in earlier to avoid blocking the main feature, but it has now been suppressed when --json is passed for cleaner machine-readable output.

Example

With --json:

$ wrangler r2 bucket info my-bucket-name --json

(⛅️ wrangler 4.18.0\n──────────────────)
{
  "name": "my-bucket-name",
  "created": "2025-06-07T15:55:22.222Z",
  "location": "APAC",
  "default_storage_class": "Standard",
  "object_count": "0",
  "bucket_size": "0 B"
}

Without --json:

$ wrangler r2 bucket info my-bucket-name

(⛅️ wrangler 4.18.0\n──────────────────)
Bucket Name: my-bucket-name  
Created At: 2025-06-07T15:55:22.222Z  
Location: APAC  
Storage Class: Standard  
Object Count: 0  
Size: 0 B

Edit (June 12, 2025)

Implemented the requested change to suppress the banner (⛅ wrangler 4.18.0) when --json is used.

$ wrangler r2 bucket info my-bucket-name

{
  "name": "my-bucket-name",
  "created": "2025-06-07T15:55:22.222Z",
  "location": "APAC",
  "default_storage_class": "Standard",
  "object_count": "0",
  "bucket_size": "0 B"
}