KAFKA-12779: KIP-740, Introduce public TaskId interface and TaskMetadata.id() API that returns it

[ableegoldman]

This PR moves the existing TaskId class to the internals package, and has it implement a new TaskId interface which just exposes the metadata fields. The interface will be part of the public API, and is returned by the new TaskMetadata.Id() API. The old TaskMetadata.taskId() method that returns a String is also deprecated in this PR

The KIP is currently under voting so this PR can't be merged yet, but it is ready to be reviewed: KIP-740

[ableegoldman]

I know this looks like it will be absolutely miserable to review since there are 109 files changed, but probably at least 100 of them are just one or two lines of change: inserting the new internals package in the import of the TaskId class, and/or migrating from the taskId() to the taskIdMetadata() APIs.

The only "real" changes are those listed in the PR description: the new and old TaskId classes plus the new TaskIdMetadata interface, and the new + deprecated APIs in TaskMetadata, ProcessorContext, and StateStoreContext. You should focus your review on those classes and skim (or even skip) the rest.

[ableegoldman]

Closed in favor of #10735