refactor!: move BlockTrackerPollingController to user-operation-controller

[mikesposito]

Explanation

BlockTrackerPollingController is being removed from @metamask/polling-controller so that the package doesn't need to depend on @metamask/network-controller.

The only consumer of the removed class is @metamask/user-operation-controller, so it has been moved there (unexported) to leave the consumer unchanged.

References

• Related to feat: auto-enable networks from config-registry #9879 due to circular dependency

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

---

Note

Medium Risk
Breaking public API removal may affect downstream packages; in-repo usage is confined to user-operation-controller with a straight import swap.

Overview
Breaking: @metamask/polling-controller no longer ships BlockTrackerPollingController / BlockTrackerPollingControllerOnly and drops its @metamask/network-controller dependency (tsconfig and package graph updated accordingly).

The block-tracker polling mixin now lives inside @metamask/user-operation-controller as a local module; PendingUserOperationTracker imports it from there instead of from @metamask/polling-controller. That implementation pulls shared polling primitives (AbstractPollingControllerBaseMixin, getKey, and related types) from the polling package’s new public exports, so behavior for the sole in-repo consumer should stay the same.

Docs/changelog and README dependency edges reflect the split; polling-controller eslint suppressions for the removed test file are dropped, and user-operation-controller coverage thresholds are relaxed slightly.

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[mikesposito]

Adding the no-changelog label as user-operation-controller has no visible consumer change

[mcmire]

LGTM!

[mcmire]

We might want to add 1 instance of explicit-function-return-type back, but for the user-operation-controller package. (If we're going to remove this package anyway, we don't need to fix this lint violation right now.)