[Dashboard] Use factory's displayName in save modal

[Heenawter]

Summary

As part of a larger navigation embeddable discussion, it was noted that there were inconsistencies between how we display the panel type between the saved object modal and the context menu action. Turns out, this is because we were using the embeddable type in the "Save to library" modal title while the context menu action uses the factory's displayName - while this coincidentally worked in most cases (maps and visualization), it does not work for Lens panels, since we want to use the proper noun "Lens" in this case rather than the saved object type "lens":

This was even more obvious with the navigation embeddable, since the saved object type is currently "navigation_embeddable" (this may change in the future):

Therefore, by switching to use the factory's displayName (if available), the saved object modal will now stay consistent with the "Edit <x>" option in the context menu for each panel.

Before	After
	No change, as expected.
	No change, as expected.

Note that, in the above "After" screenshots, Links is still capitalized unnecessarily - this is because, if we change the factory's displayName to be the lowercase "links", this fixes the modal but it also impacts the item in the add panel context menu and the panel actions context menu, like so:

Add panel context menu	Panel actions context menu

This is because the link embeddable is not currently registered as a "visualization" and so the "Add panel" context menu logic is handled as part of getEmbeddableFactoryMenuItem in ./src/plugins/dashboard/public/dashboard_app/top_nav/editor_menu.tsx rather than getVisTypeMenuItem (this could potentially be fixed by #162840 since we have custom logic for displaying aliases). While the lowercase "links" in the panel actions context menu is desired, it is not desirable to have the lowercase "links" in the add panel context menu - however, it is not currently possible to change one without changing the other.

Note that this is also true for the "Image" embeddable - by changing the displayName of the image factory from "Image" to "image", the "Edit" panel actions context menu item would be displayed correctly as "Edit image" (currently, it is "Edit Image") but the lowercase "image" would also be displayed in the add panel context menu, which is undesirable.

It will require a larger refactor to fix these inconsistencies, so it should be addressed separately.

Checklist

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support

For maintainers

• This was checked for breaking API changes and was labeled appropriately

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: bd1d6fb

Metrics [docs]

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
embeddable	64.7KB	64.9KB	+139.0B

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@elasticmachine merge upstream

cc @Heenawter

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