Derive runtime config defaults from javy_config::Config

[jeffcharles]

Description of the change

Centralizes the default JS runtime configuration in the javy_config::Config struct's Default implementation. This will also keep the JS runtime command line settings default values in sync with the javy_config::Config default values.

Why am I making this change?

Prior there were a few different places in the code that would set configuration properties to different values depending on the path through the code (e.g., some used Config::all, others disabled OVERRIDE_JSON_PARSE_AND_STRINGIFY).

Checklist

• I've updated the relevant CHANGELOG files if necessary. Changes to javy-cli and javy-core do not require updating CHANGELOG files.
• I've updated the relevant crate versions if necessary. Versioning policy for library crates
• I've updated documentation including crate documentation if necessary.