Add optional parallel eager loading

[elpete]

Closes #55

Issue review

Recommendation: 7/10 — implement as opt-in. Independent eager-load branches can benefit from concurrency when database latency and hydration work dominate, especially for several unrelated top-level relationships. It should not be the default: concurrency consumes more database connections and CPU, and does not help a single relationship or necessarily improve low-latency queries.

Implementation

• adds an optional parallel boolean to with, e.g. .with( [ "author", "comments" ], true )
• uses ColdBox's AsyncManager and an application-wide bounded executor; applications can supply one with parallelEagerLoadingExecutor, otherwise Quick creates and owns a fixed executor
• caps each query's parallelEagerLoadingMaxThreads by the configured executor's maximum pool size
• performs retrieval, entity hydration, transformations, nested eager loading, and branch-local collection construction on workers
• keeps matching and mutation of the original parent entities, plus top-level quickRelationshipLoaded, on the calling thread
• hydrates polymorphic branches on workers without allowing them to mutate the original parents
• gives every worker an isolated ColdBox request context and preserves the BoxLang application mappings and default datasource needed during hydration
• propagates worker failures instead of returning partial relationship data, cancels outstanding work on failure or timeout, and avoids parallel work inside transactions
• retains the existing sequential path by default and for a single top-level relationship

Validation

• focused relationship/module suite on Lucee 5: 59 passed, 0 failed, 0 errors
• focused relationship/module suite on BoxLang 1: 59 passed, 0 failed, 0 errors
• full Lucee 5 suite: 624 passed, 0 failed, 0 errors, 3 skipped
• full BoxLang 1 suite: 625 passed, 0 failed, 0 errors, 2 skipped
• box run-script format:check
• git diff --check

Uses qb@14.0.0-beta.3.