fix: gather engine_adapters from all projects

[etonlels]

Trying to use sqlmesh render with multiple projects can fail with Gateway '{gateway}' not found in the available engine adapters. This is because the Context.engine_adapters only looks at self.config instead of self.configs. This PR modifies the definition of engine_adapters to look at all projects, thereby avoiding this issue.

[themisvaltinos]

Thanks for your contribution it looks good, can you also add a test for this?

For example in tests/core/test_integration.py something like:

def test_engine_adapters_multi_repo_all_gateways_gathered(copy_to_temp_path):

    paths = copy_to_temp_path("examples/multi")
    repo_1_path = f"{paths[0]}/repo_1"
    repo_2_path = f"{paths[0]}/repo_2"

    # Add an extra gateway to repo_2's config
    repo_2_config_path = f"{repo_2_path}/config.yaml"
    with open(repo_2_config_path, "r") as f:
        config_content = f.read()

    modified_config = config_content.replace(
          "default_gateway: local",
          """  extra:
    connection:
      type: duckdb
      database: extra.duckdb

default_gateway: local"""
      )

    with open(repo_2_config_path, "w") as f:
        f.write(modified_config)

    # Create context with both repos but using the repo_1 path first
    context = Context(paths=[repo_1_path, repo_2_path], gateway="memory")

    # Verify all gateways from both repos are present
    adapters = context.engine_adapters
    expected_gateways = {"local", "memory", "extra"}
    missing = expected_gateways - set(adapters.keys())
    assert not missing

[etonlels]

can you also add a test for this?

Certainly. Thank you for the starting point 🙏