feat(cloudwatch): add CloudWatch client

[thisisabhash]

Issue #

NA

Description

What Changed

New: AmplifyCloudWatchLoggingClient

• Standalone client conforming to AmplifyFoundation.LogSinkBehavior
• Namespace-based logging with automatic batching and local file persistence
• Configurable flush strategy, log level constraints, and per-user filtering
• Single shared CloudWatchLogsClient instance (created once in init)
• Per-client file isolation via storagePathIdentifier (prevents collisions between multiple client instances)
• Per-client CloudWatch stream isolation (stream name includes client identifier)
• Combine-based events publisher for observing flush/write failures
• @_spi(AmplifyExperimental) public API surface

New: InternalCloudWatchLogging shared module

• Extracted common infrastructure used by both the plugin and client:
  • LogFile, LogRotation, LogActor (persistence)
  • LogBatch, LogBatchConsumer, LogBatchProducer, LogEntryRepresentable (protocols)
  • LoggingNetworkMonitor (network connectivity)
  • CloudWatchConstants (SDK limits)
• All APIs use package access level
• Plugin and client both depend on this module

Modified: AWSCloudWatchLoggingPlugin

• Now imports InternalCloudWatchLogging for shared persistence and networking types
• Removed duplicated files (replaced with shared module imports)
• Restored original AWSCloudWatchLoggingMonitorDelegate public API
• No behavior changes

Tests

• 50+ unit tests for the client covering: LogEntry, LogFile, LogRotation, LogActor, RotatingLogger, RotatingLogBatch, CloudWatchLoggingConsumer, CloudWatchLoggingFilter, CloudWatchLoggingMonitor, session isolation, and the client class itself
• Integration test host app with tests for flush, enable/disable, and multi-client stream isolation
• All existing plugin tests pass (59/60, 1 pre-existing flaky timeout)
• Added AmplifyCloudWatchLoggingClient to CI unit test workflow

Package.swift

• New targets: InternalCloudWatchLogging, AmplifyCloudWatchLoggingClient (updated), AmplifyCloudWatchLoggingClientTests
• New library product: AmplifyCloudWatchLoggingClient
• Updated dependencies for AWSCloudWatchLoggingPlugin and AWSCloudWatchLoggingPluginTests

Testing

• swift test --filter AmplifyCloudWatchLoggingClientTests — 50+ tests, all pass
• swift test --filter AWSCloudWatchLoggingPluginTests — 60 tests, 59 pass (1 pre-existing flaky timeout)
• Integration tests verified manually via Xcode host app

Directory Structure

AmplifyClients/AmplifyCloudWatchLoggingClient/
├── Sources/
│   ├── AmplifyCloudWatchLoggingClient.swift
│   ├── CloudWatchLoggingError.swift
│   ├── CloudWatchLoggingSession.swift
│   ├── CloudWatchLoggingSessionController.swift
│   ├── CloudWatchLogsClientProtocol.swift
│   ├── Configuration/
│   ├── Consumer/
│   ├── Domain/
│   ├── Persistence/
│   ├── Producer/
│   └── Support/
├── Tests/
│   ├── UnitTests/
│   └── IntegrationTests/CloudWatchLoggingClientHostApp/

AmplifyPlugins/Internal/Sources/InternalCloudWatchLogging/
├── Domain/ (LogBatch, LogBatchConsumer, LogBatchProducer, LogEntryRepresentable)
├── Persistence/ (LogActor, LogFile, LogRotation)
└── Support/ (CloudWatchConstants, LoggingNetworkMonitor)

General Checklist

• Added new tests to cover change, if needed
• Build succeeds with all target using Swift Package Manager
• All unit tests pass
• All integration tests pass
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• Documentation update for the change if required
• PR title conforms to conventional commit style
• New or updated tests include Given When Then inline code documentation and are named accordingly testThing_condition_expectation()
• If breaking change, documentation/changelog update with migration instructions

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.