WIP [jnigen] Config API update

[liamappelbe]

Update JNIgen's config API to align it with the proposed FFIgen API.

[github-actions]

Package publishing

If you have publishing permissions, you can use the links below to publish the changes after merging this PR.

Package	Version	Status	Publish tag (post-merge)
package:code_assets	1.3.0-wip	WIP (no publish necessary)
package:data_assets	0.20.0	already published at pub.dev
package:ffi	2.2.0	already published at pub.dev
package:hooks	2.2.0-wip	WIP (no publish necessary)
package:hooks_runner	1.6.2-wip	WIP (no publish necessary)
package:jni_flutter	1.0.2	already published at pub.dev
package:jni_util	1.0.0	already published at pub.dev
package:native_toolchain_c	0.19.4-wip	WIP (no publish necessary)
package:record_use	1.1.0	ready to publish	record_use-v1.1.0
package:swift2objc	0.3.0-wip	WIP (no publish necessary)
package:swiftgen	0.1.3	already published at pub.dev

Documentation at https://github.com/dart-lang/ecosystem/wiki/Publishing-automation.

[github-actions]

PR Health

Changelog Entry ❗

Package	Changed Files
package:jni	pkgs/jni/lib/src/core_bindings.dart
package:jni_flutter	pkgs/jni_flutter/lib/src/generated_plugin.dart

Changes to files need to be accounted for in their respective changelogs.

This check can be disabled by tagging the PR with skip-changelog-check.

API leaks ✔️

The following packages contain symbols visible in the public API, but not exported by the library. Export these symbols or remove them from your publicly visible API.

Package	Leaked API symbol	Leaking sources

This check can be disabled by tagging the PR with skip-leaking-check.

Breaking changes ✔️

Package	Change	Current Version	New Version	Needed Version	Looking good?
jni_flutter	None	1.0.2	1.0.2	1.0.2	✔️
jni	None	1.0.3	1.0.3	1.0.3	✔️

This check can be disabled by tagging the PR with skip-breaking-check.