WL#17234: Make "MTA: extended applier statistics" community edition

# EXECUTIVE SUMMARY

This worklog enables the `MTA: Extended Applier Statistics` feature in the MySQL
Community Edition build, making this replication observability capability
available beyond the Enterprise edition.
The change improves visibility into multi-threaded replication behavior for
Community Edition users, aligning feature availability across editions without
altering existing functionality or behavior.

# USER STORIES

* As a MySQL Community Edition user who operates multi-threaded replication,
  I want access to extended applier statistics for the MTA, so that I can
  better observe, analyze, and troubleshoot replication performance and
  behavior without requiring the Enterprise edition.

# FUNCTIONAL REQUIREMENTS

FR-01. The `MTA: Extended Applier Statistics` feature shall be available in the
       MySQL Community Edition build.

FR-02. The feature shall expose the same set of MTA extended applier statistics
       in the Community Edition as currently available in the Enterprise
       Edition.

FR-03. The feature shall be enabled by default in Community Edition builds,
       consistent with current behavior in Enterprise Edition builds.

FR-04. Existing interfaces (e.g., performance schema tables, status variables,
       or instrumentation points) used to expose the statistics shall remain
       unchanged.

FR-05. The change shall be transparent to users upgrading from earlier versions,
       with no configuration changes required.

FR-06. There shall be no functional regressions or behavior changes to
       replication, applier threads, or performance when the feature is enabled.

FR-07. The implementation shall maintain compatibility across supported
       platforms for Community Edition builds.

# NON-FUNCTIONAL REQUIREMENTS

NFR-01. The change shall not introduce any measurable performance regression in
        replication or applier threads.

NFR-02. Logging, error handling, and diagnostics behavior shall remain
        unchanged.

# Summary of the approach

This worklog makes the existing `MTA: Extended Applier Statistics` feature
available in the MySQL Community Edition build.
The implementation reuses the current instrumentation and logic without
introducing new functionality. The change is limited to build and packaging
adjustments to ensure the feature is included and enabled in Community Edition
binaries, consistent with its behavior in the Enterprise Edition.

No changes are made to replication logic, statistics collection, or exposure
mechanisms.

# Security context

No applicable changes on security context.

# Observability

Observability remains unchanged.

# Upgrade/downgrade and cross-version replication

Upgrades from earlier Community Edition versions will automatically gain access
to the extended applier statistics, without requiring configuration changes.

Downgrades behave as before; statistics not supported by the downgraded version
will simply be unavailable.

Cross-version replication behavior is unchanged.

There is no impact on replication compatibility between Community and
Enterprise Edition instances.

# User interface

No new user interfaces are introduced.

Existing SQL interfaces, system tables, and performance schema views remain
unchanged.

Users interact with the feature using the same queries and tools as before.

# Deployment and installation

The change affects build and packaging only.

Community Edition binaries will include the feature by default.

No special installation steps are required.

Deployment workflows remain unchanged.

# Protocol

No protocol changes.

# Failure Model Specification

No new failure modes are introduced.

# Behavior Changes

The only behavior change is the availability of extended applier statistics in
Community Edition.

There are no changes to replication behavior, statistics semantics, or default
configurations.

Enterprise Edition behavior remains unchanged.