feat: infer shard key from primary key

Summarize the changes

• feat: infer shard key from primary key

Ensure that

• New code is covered by unit and integration tests.

• Related issues would be automatically closed with gitlab's closing pattern (Closes #1, #2).

• Public modules are documented (check the rendered version with cargo doc --open).

• (if PEST grammar is changed) EBNF grammar reflects these changes (check the result with railroad diagram generator.

• picodata MR: picodata!1194 (merged)

Next steps

• Cherry-pick to: none
• Update sbroad submodule in picodata/picodata.
• (if EBNF grammar is changed) create a follow-up issue in picodata/docs.