Bump golang + golangci-lint

[sameerforge]

What this PR does / why we need it:

This PR fixes golang CVEs by updating golang to 1.25.6.

Which issue(s) this PR fixes:

─────────┬────────────────┬──────────┬────────┬───────────────────┬─────────────────┬──────────────────────────────────────────────────────────────┐
│ Library │ Vulnerability  │ Severity │ Status │ Installed Version │  Fixed Version  │                            Title                             │
├─────────┼────────────────┼──────────┼────────┼───────────────────┼─────────────────┼──────────────────────────────────────────────────────────────┤
│ stdlib  │ CVE-2025-61726 │ HIGH     │ fixed  │ v1.25.5           │ 1.24.12, 1.25.6 │ golang: net/url: Memory exhaustion in query parameter        │
│         │                │          │        │                   │                 │ parsing in net/url                                           │
│         │                │          │        │                   │                 │ https://avd.aquasec.com/nvd/cve-2025-61726                   │
│         ├────────────────┤          │        │                   │                 ├──────────────────────────────────────────────────────────────┤
│         │ CVE-2025-61728 │          │        │                   │                 │ golang: archive/zip: Excessive CPU consumption when building │
│         │                │          │        │                   │                 │ archive index in archive/zip                                 │
│         │                │          │        │                   │                 │ https://avd.aquasec.com/nvd/cve-2025-61728                   │
│         ├────────────────┼──────────┤        │                   │                 ├──────────────────────────────────────────────────────────────┤
│         │ CVE-2025-61730 │ MEDIUM   │        │                   │                 │ During the TLS 1.3 handshake if multiple messages are sent   │
│         │                │          │        │                   │                 │ in records...                                                │
│         │                │          │        │                   │                 │ https://avd.aquasec.com/nvd/cve-2025-61730                   │
└─────────┴────────────────┴──────────┴────────┴───────────────────┴─────────────────┴──────────────────────────────────────────────────────────────┘

Fixes #

Does this PR introduce a user-facing change?

Additional Notes for your reviewer:

Review Checklist:

• Follows the developer guidelines
• Relevant tests are added or updated
• Relevant docs in this repo added or updated
• Relevant carvel.dev docs added or updated in a separate PR and there's
  a link to that PR
• Code is at least as readable and maintainable as it was before this
  change

Additional documentation e.g., Proposal, usage docs, etc.: