Feature: Expose Public GC Configuration API

[workonlly]

Feature Description

Summary

Expose a public API to configure Boa’s garbage collector (GC) at runtime. This allows embedders and advanced users to tune memory management by setting allocation thresholds and used-space triggers.

Note: This aims to resolve the GC configuration TODO currently located in the engine initialization path (e.g., lib.rs:63).

Motivation

• Enables embedders to control GC behavior for different workloads.
• Provides the required groundwork for future GC redesigns and benchmarking.
• Aligns with best practices in other major JavaScript engines (e.g., V8, SpiderMonkey).

Requirements

• Create a public GcConfig struct with fields for threshold and used-space percentage.
• Implement public gc_config() and set_gc_config() functions to get/set the current thread-local GC config.
• Integrate with ContextBuilder so embedders can set the GC configuration at context creation.
• Add unit tests for config normalization and roundtrip validation.
• Add rustdoc documentation for the new API.

Acceptance Criteria

• Users can successfully set and get the GC config at runtime.
• Setting the config via ContextBuilder correctly applies to the newly created context.
• All tests pass and documentation is successfully generated.

Example code
This Rust code should work and allow the embedder to successfully configure the GC upon context creation:

use boa_engine::ContextBuilder;
use boa_engine::gc::GcConfig;

let custom_gc_config = GcConfig::new(10_000_000, 80);
// or you can: GcConfig::default().with_threshold(10_000_000).with_used_space_percentage(80);

let mut context = ContextBuilder::new()
    .gc_config(custom_gc_config)
    .build()
    .expect("Failed to build context");

// Also a point to remmember The engine should now respect the custom thresholds during execution.

[Veercodeprog]

@workonlly could you assign this to me?

[workonlly]

firstly can you share your approach

[workonlly]

in which file do have to do changes

[Veercodeprog]

in which file do have to do changes
we have to expose our api to configure Gc,
we have to work mainly with GcConfig that is in core/gc/src/lib.rs