core-*-api: backport support for external route ref default targets + config route binding

[Rugvip]

Hey, I just made a Pull Request!

The new frontend system supports route binding through static configuration, for example:

app:
  routes:
    bindings:
      catalog.createComponent: catalog-import.importPage

It also lets you define default targets for external route references, for example:

export const registerComponentRouteRef = createExternalRouteRef({
  optional: true,
  defaultTarget: 'catalog-import.importPage',
});

This adds support for both of these features in the existing frontend system.

✔️ Checklist

• A changeset describing the change and affected packages. (more info)
• Added or updated documentation
• Tests for new functionality and regression tests for bug fixes
• Screenshots attached (for UI changes)
• All your commits have a Signed-off-by line in the message. (more info)

[backstage-goalie]

Changed Packages

Package Name	Package Path	Changeset Bump	Current Version
example-app	packages/app	none	v0.2.97-next.2
@backstage/core-app-api	packages/core-app-api	patch	v1.12.4
@backstage/core-compat-api	packages/core-compat-api	patch	v0.2.5-next.1
@backstage/core-plugin-api	packages/core-plugin-api	patch	v1.9.2
@backstage/plugin-api-docs	plugins/api-docs	patch	v0.11.5-next.2
@backstage/plugin-catalog-graph	plugins/catalog-graph	patch	v0.4.5-next.2
@backstage/plugin-catalog	plugins/catalog	minor	v1.20.0-next.2
@backstage/plugin-org	plugins/org	patch	v0.6.25-next.2
@backstage/plugin-scaffolder	plugins/scaffolder	minor	v1.19.4-next.2

[github-actions]

Thank you for contributing to Backstage! The changes in this pull request will be part of the 1.28.0 release, scheduled for Tue, 18 Jun 2024.

[github-actions]

Uffizzi Cluster pr-24698 was deleted.

[Rugvip]

Merged by mistake, reverted and replaced by #24777