pallet-identity-migrator Becomes a Separate Crate

[asiniscalchi]

This PR separates pallet-identity-migrator into its own crate while keeping the refactor transparent to the code outside polkadot-runtime-common. By re-exporting the pallet in polkadot-runtime-common, external references remain unchanged, preserving backward compatibility and minimizing impact on the wider Polkadot codebase.

Changes Summary:

• Crate Creation: Extracted pallet-identity-migrator to a standalone crate, including a dedicated Cargo.toml for dependencies and configurations.
• Re-export in polkadot-runtime-common: To maintain existing code paths, pallet-identity-migrator is re-exported in polkadot-runtime-common, making the refactor invisible to external users.
• Dependency Adjustments: Updated Cargo.toml in polkadot-runtime-common and top-level workspace to reflect the new crate path for pallet-identity-migrator.

This approach enhances modularity without requiring any changes from the rest of the Polkadot codebase.

[paritytech-cicd-pr]

The CI pipeline was cancelled due to failure one of the required jobs.
Job name: cargo-clippy
Logs: https://gitlab.parity.io/parity/mirrors/polkadot-sdk/-/jobs/5703514

[asiniscalchi]

The CI pipeline was cancelled due to failure one of the required jobs. Job name: cargo-clippy Logs: https://gitlab.parity.io/parity/mirrors/polkadot-sdk/-/jobs/5703514

Clippy is giving errors on this :

error: field `0` is never read
   --> polkadot/runtime/parachains/src/inclusion/mod.rs:389:28
    |
389 |     ProcessedDownwardMessages(dmp::ProcessedDownwardMessagesAcceptanceErr),
    |     ------------------------- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |     |
    |     field in this variant
    |
    = note: `-D dead-code` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(dead_code)]`
help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
    |
389 |     ProcessedDownwardMessages(()),
    |                               ~~

error: field `0` is never read
   --> polkadot/runtime/parachains/src/inclusion/mod.rs:391:17
    |
391 |     UpwardMessages(UmpAcceptanceCheckErr),
    |     -------------- ^^^^^^^^^^^^^^^^^^^^^
    |     |
    |     field in this variant
    |
help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
    |
391 |     UpwardMessages(()),
    |                    ~~

error: field `0` is never read
   --> polkadot/runtime/parachains/src/inclusion/mod.rs:395:15
    |
395 |     OutboundHrmp(hrmp::OutboundHrmpAcceptanceErr),
    |     ------------ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |     |
    |     field in this variant
    |
help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
    |
395 |     OutboundHrmp(()),
    |                  ~~

polkadot-sdk/polkadot/runtime/parachains/src/inclusion/mod.rs

Lines 382 to 396 in 8d30534

	enum AcceptanceCheckErr<BlockNumber> {
	HeadDataTooLarge,
	/// Code upgrades are not permitted at the current time.
	PrematureCodeUpgrade,
	/// The new runtime blob is too large.
	NewCodeTooLarge,
	/// The candidate violated this DMP acceptance criteria.
	ProcessedDownwardMessages(dmp::ProcessedDownwardMessagesAcceptanceErr),
	/// The candidate violated this UMP acceptance criteria.
	UpwardMessages(UmpAcceptanceCheckErr),
	/// The candidate violated this HRMP watermark acceptance criteria.
	HrmpWatermark(hrmp::HrmpWatermarkAcceptanceErr<BlockNumber>),
	/// The candidate violated this outbound HRMP acceptance criteria.
	OutboundHrmp(hrmp::OutboundHrmpAcceptanceErr),
	}

What's the ratio of those params not being used ?

[ggwpez]

This is a one-off crate that will be deleted soon, any effort here is pretty much wasted...