Remove RecursiveDataStructureTraverser

[schlessera]

This PR removes the RecursiveDataStructureTraverser class from the wp-cli/entity-command package and sets the package up to reuse it from the framework instead.

Note: Pushing first with the removal only to show how it fails before fixing the distribution aspect of it.

[schlessera]

@danielbachhuber , @swissspidy some added context here to explain how this works:
The new \WP_CLI\Traverser\RecursiveDataStructureTraverser in the framework is not yet part of a tagged release, it is only included in the main branch so far.

However, given that:

• the stability requirements of this package have been set to dev =>

  entity-command/composer.json

  Line 199 in b5846bf

  "minimum-stability": "dev",

• the wp-cli/wp-cli has a branch alias that is correctly set => https://github.com/wp-cli/wp-cli/blob/f37504278b39fc0265bf5a8936c345bc737ee0a1/composer.json#L40

... we can tell Composer to pull in version 2.10+ of the framework. It will accept dev-main to represent a non-stable version of 2.10, and the dev stability requirements will allow that version to be used for wp-cli/entity-command's requirements => a6d96ee#diff-d2ab9925cad7eac58e0ff4cc0d251a937ecf49e4b6bf57f8b95aab76648a9d34R15

This effectively means that the wp-cli/entity-command will pull in dev-main and assume it is v2.10+ (and all other packages have been set up to work correctly with this).

Then, once we will release a tagged version 2.10.0 for the wp-cli/wp-cli framework, the fact that the wp-cli/entity-command has prefer-stable set to true means that it will revert back to a stable, tagged version of 2.10.0 and all future versions as soon as possible =>

entity-command/composer.json

Line 200 in b5846bf

"prefer-stable": true,

/cc @thelovekesh

[danielbachhuber]

@schlessera Thanks for explaining all of that!