Add async QQL support with AsyncConnection and AsyncExecutor, plus sync
and async batching helpers for running multiple statements through one
programmatic API. Introduce BEGIN BATCH syntax, parameterized query
helpers, and optional gRPC connection settings.

Refactor shared parser and executor logic into qql.utils so sync and
async paths can reuse filter conversion, vector shaping, topology parsing,
batch grouping, and search parsing helpers.

Update tests and docs for async usage, batching, parameterized queries,
gRPC configuration, and batch block execution.

…ll handling

… management and null support

…er building

…grpc-async-support