Release langchain-core==0.2.12

Changes since langchain-core==0.2.11

core: release 0.2.12 (#23991)
core[minor],community[patch],standard-tests[patch]: Move InMemoryImplementation to langchain-core (#23986)
core[minor],community[minor]: Upgrade all @root_validator() to @pre_init (#23841)
core[patch]: Use InMemoryChatMessageHistory in unit tests (#23916)
core[patch]: Clarify upsert response semantics (#23921)
core[patch]: Add comment to clarify aadd_documents (#23920)
core, anthropic[patch]: support streaming tool calls when function has no arguments (#23915)
core[minor]: Add Graph Store component (#23092)
core: docstrings load (#23787)
core[minor]: add upsert, streaming_upsert, aupsert, astreaming_upsert methods to the VectorStore abstraction (#23774)
core[patch]: Fix typo in docstring (graphm -> graph) (#23910)
core: docstrings outputs (#23889)
core: docstrings prompts (#23890)
core[patch]: Accounting for Optional Input Variables in BasePromptTemplate (#22851)
core[patch]: Fix logic in BaseChatModel that processes the llm string that is used as a key for caching chat models responses (#23842)
core[minor]: update conversion utils to handle RemoveMessage (#23840)
core[patch]: Speed up unit tests for imports (#23837)
core[patch]: extract input variables for path and detail keys in order to format an ImagePromptTemplate (#22613)
core[patch]: docstrings output_parsers (#23825)
infra: update mypy 1.10, ruff 0.5 (#23721)
[Core] Unify function schema parsing (#23370)
core: docstrings indexing (#23785)
core: docstrings messages (#23788)