feat!: refactor `seo` to use GraphQL Interfaces

[justlevine]

What

This PR refactors how SEO data is added to the schema. In particular the seo field is now of type RankMathSeo and is added using the NodeWithRankMathSeo interface.

Why

• DRYer and indeterminate queries (e.g. with nodeByUri() ).
• Lays the foundation for Object-specific SEO fields.

How

• feat!: Rename RankMathBaseSeoFields interface to `RankMathSeo.
• feat!: Change seo field type to RankMathoSeo interface and impelement with NodeWithRankMathSeo interface.
• feat!: Change RankMathCommentNodeSeo from GraphQL object to interface.
• dev: add the following WordPress filters: graphql_seo_model_class, graphql_seo_resolved_type_name, graphql_seo_types_with_seo.

Testing Instructions

query MyNodeByUriQuery( $uri: String ) {
  nodeByUri( uri: $uri ) {
    ... on NodeWithRankMathSeo {
      seo {
        breadcrumbs {
          title
          url
          isHidden
        }
        breadcrumbTitle
        canonicalUrl
        description
        focusKeywords
        fullHead
        jsonLd {
          raw
        }
        robots
        title
        ... on RankMathContentNodeSeo {
          isPillarContent
          seoScore {
            score
          }
        }
      }
    }
  }
}

Additional Info

Checklist:

• [x] My code is tested to the best of my abilities.
• [x] My code follows the WordPress Coding Standards.
• [x] My code has proper inline documentation.
• [x] I have added unit tests to verify the code works as intended.
• [x] The changes in this PR have been noted in CHANGELOG.md