Add heartbeat() method to AmqpQueueProvider (#28)

* Add heartbeat() method to AmqpQueueProvider

Allows callers to explicitly trigger a heartbeat check on a specific
connection mode or all active connections, disconnecting on missed
heartbeats so the next operation triggers a reconnect.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* Improve heartbeat tests to verify code path execution

Add heartbeat check counter to AmqpMockProvider to assert that
_heartbeat() is actually invoked rather than short-circuited.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* Add PubSub test coverage and fix gRPC error code handling

Add integration tests for GooglePubSubProvider against the PubSub emulator.
Fix auto_create not working on gRPC transport - the code compared exception
codes against HTTP status codes (404/409) but the Google Cloud PHP library
passes gRPC codes (5/6) when using gRPC transport.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* Fix CI: run PubSub emulator as a step instead of service

Docker entrypoint doesn't support multi-word commands as a single string.
Run the emulator via docker run in a step with a health check wait.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* Fix CI: add grpc extension for PubSub emulator on PHP 8.x

PubSub v2 requires the grpc extension to use the emulator - without it,
the REST transport validates credentials before checking the emulator flag.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* remove grpc

* Fix PubSub emulator auth on cloud-pubsub v2

PubSub v2 validates credentials before checking the emulator flag.
Pass InsecureCredentials when PUBSUB_EMULATOR_HOST is set and no
explicit credentials are configured.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

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Co-authored-by: Claude Opus 4.6 (1M context) <[email protected]>

Update php-amqplib (#27)

* update php-amqplib

* add github action tests

* drop circleci

* update phpunit

* drop windows, and older php

* update test class

* add coverage checker

* update xml

* phpunit 9

update to use packaged/log (#26)

Heartbeat tests (#25)

retry on missed heartbeats (#24)

v1 helpers also supported (#23)

interpret string values as bools (#22)

support heartbeat via configuration (#21)

Explicit Exceptions (#20)

* added exceptions

* replaced generic exceptions with more specific ones

upgrade to latest amqp version, enabling heartbeats (#18)

* upgrade to latest amqp version, enabling heartbeats

* add sockets module