[Refactor] XContent from common to core namespace

[nknize]

XContent namespace refactor from common -> core is going to be merged to opensearch/2.x which will break the 2.x build. This issue is for refactoring XContent imports from the common to core namespace after the core namespace change is merged.

Depends on opensearch-project/OpenSearch#6470

[nknize]

opensearch-project/OpenSearch#6470 merged

[DarshitChanpura]

Hey team, Is the still on-track for being merged for 2.7? The code-freeze for v2.7.0 is on Apr 17.

[dblock]

@DarshitChanpura looks like it per opensearch-project/OpenSearch#6841 (comment)

[mch2]

no reply, closing as 2.7 has shipped with this change.