Add bolt+routing with automatic failover and retry support

[mattkjames7]

Extends the mgclient API to include bolt+routing with automatic failover and retry logic.

This includes:

• Functions to parse the routing table in order to view the cluster's topology.
• Error classification: Bolt TransientError/low-level transport failures indicated by int mg_error_is_transient(in error) -> tells us whether a request should be retried.
• Added a router:
  • mg_router_config_* functions for configuring session params (e.g. SSL, resolver) and retry policy (retries, backoff).
  • Resolver for mapping advertised "host:port" addresses to reachable ones (e.g. for working with port forwards).
  • mg_router_* functions for creating/destroying the router; connecting read/write sessions; routing table (fetch, refresh).
• Managed transactions by passing work functions to mg_router_execute_read and mg_router_execute_write functions.

[Copilot]

Pull request overview

This PR extends mgclient with client-side routing support for Memgraph HA clusters by introducing routing table parsing, target selection with optional address resolution, transient error classification, and a router API that can connect to READ/WRITE servers and execute managed transactions with retry/backoff.

Changes:

• Added public routing APIs to mgclient.h (routing table, transient error classification, resolver interface, router config/router lifecycle, managed execute helpers).
• Implemented routing table parsing, coordinator refresh + failover, read round-robin selection, and managed execute retry/backoff in src/mgrouting.c (+ internal test seam in src/mgrouting.h).
• Added routing unit/integration tests + example and updated CI to optionally spin up an HA cluster and exercise routing.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tests/routing.cpp	New routing/execute tests (includes cluster-gated cases).
tests/encoder.cpp	Updates GTest instantiation macros (modernization).
tests/decoder.cpp	Updates GTest instantiation macros (modernization).
tests/CMakeLists.txt	Adds routing test + builds routing example.
src/mgrouting.h	Internal routing helpers exposed for white-box tests.
src/mgrouting.c	Core routing/router implementation (refresh/connect/execute).
src/CMakeLists.txt	Adds routing implementation to build.
include/mgclient.h	Public API additions for routing/router/retry.
examples/routing.c	New example demonstrating client-side routing usage.
.github/workflows/ci.yml	Adds optional HA cluster setup and routing example run.

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