Add pallet-rate-limiting

[ales-otf]

Description

TBD

How to review:

As much as I could I tried to organize this PR in a way, where each major change is represented by a single commit and I tried avoiding small commits as much as possible, so you could refer the commit history and review changes related to particular limits.

pallet-rate-limiting has detailed module-level documentation. Refer it to understand the main concepts.

1. To review how the data is migrated: runtime/src/migrations/rate_limiting::commits. This is where you'll find all that considered "legacy" rate-limiting. You can then check each migration from the "list" separately.
2. To review if the behavior is covered correctly: the migration above + runtime/src/rate_limiting. There you'll find the resolver implementations and can review how different calls were bypassed, adjusted to tempo and scoped (for limits - only by NetUid, for last-seen timestamp - different cases).
3. For proof of working and behavioral correctness: runtime/tests/rate_limiting. This is the integration tests on the extrinsic level, where transaction extensions are involved. You can verify on the behavioral level if the rate-limiting is consistent with legacy and whether all cases are covered.

Related Issue(s)

• Closes #[issue number]

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please describe):

Breaking Change

If this PR introduces a breaking change, please provide a detailed description of the impact and the migration path for existing applications.

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have run cargo fmt and cargo clippy to ensure my code is formatted and linted correctly
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Screenshots (if applicable)

Please include any relevant screenshots or GIFs that demonstrate the changes made.

Additional Notes

Please provide any additional information or context that may be helpful for reviewers.