Revert PR #31 (V0.51 exaforce rebase)

[sundaresanr]

Summary

Reverts the squashed "V0.51 exaforce rebase" merge (#31, commit `d9a1a8d3`). That merge brought forward the full v0.45-exaforce patch set onto v0.51 but carried several pieces that don't build on v0.51:

• `src/sources/azure_blob/queue.rs` + `src/azure/mod.rs` were written against azure-core 0.21; upstream v0.51 bumped to azure-core 0.25.
• Cargo.lock drifted (pulsar 6.3.1 → 6.5.0, which needs `ProducerOptions` fields the sink doesn't set).
• `lib/codecs/src/encoding/serializer.rs` had missing Parquet imports + a Rust-2024 `ref mut` in `parquet.rs`.
• `src/codecs/encoding/config.rs` accidentally dropped `configurable_component` import.

The net result: `v0.51-exaforce` has been red on every publish run since Nov 2025.

Plan after this merges

Restores `v0.51-exaforce` to pristine upstream v0.51. A follow-up PR will port only the parquet codec (the one exaforce-specific piece actually used in production). The azure_blob queue source and `impersonated_service_account` GCP auth — both confirmed unused in Vector configs — won't be ported.

This is cleaner than stripping azure/gcp back off on top of the existing merge: the v0.51-exaforce branch ends up as "upstream v0.51 + parquet codec" with no dead code in history, making future upstream rebases much easier.