feat: Add ARM64 support for yq and PostgreSQL packages

[ZPascal]

Summary

• Store two arch-keyed yq blobs (postgres-yq-amd64-*, postgres-yq-arm64-*) in the blobstore instead of a single amd64 blob; select the correct one at deploy time via uname -m
• Fix postgres-15/16/17/18 packaging scripts to add an explicit aarch64 branch, preventing ARM64 VMs from incorrectly falling into the legacy 32-bit (-m32) path
• Fix hardcoded ICU library path in postgres-16/17/18 packaging from /usr/lib/x86_64-linux-gnu to /usr/lib/aarch64-linux-gnu on ARM64
• Update bump-yq-packages CI task to verify SHA-256 and upload blobs for both architectures

Test Plan

• Verify bump-packages pipeline job runs cleanly and produces two yq blobs in config/blobs.yml (postgres-yq-amd64-* and postgres-yq-arm64-*)
• Deploy postgres-release to an x86_64 BOSH VM and confirm PostgreSQL and yq work correctly (no regression)
• Deploy postgres-release to an ARM64 BOSH VM and confirm PostgreSQL and yq install and run correctly

Depends on

• RFC: ARM64 (aarch64) Architecture Support for Cloud Foundry community#1530