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## Description
ref: https://github.com/cosmos/cosmos-sdk/issues/9237, https://github.com/cosmos/cosmos-sdk/discussions/9156
This is the first step towards the migration of the [Table-Store (ORM) package](c99dbedd1f/orm) currently in regen-ledger into the SDK. This won't be exposed as a public API to start with but rather be internal to `x/group`.
This first PR brings these core concepts:
- `table` is the high level object for storage mapper functionality where entities are stored by an unique identifier called `RowID`
- `Indexable` types can be used to setup new tables.
There will be follow-up PRs for adding the following features:
- table types with auto-incrementing `uint64` primary keys and natural primary keys
- secondary indexes
- iterator and pagination
- import/export genesis
---
### Author Checklist
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- [ ] added a changelog entry to `CHANGELOG.md` _not applicable_
- [x] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [x] updated the relevant documentation or specification
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### Reviewers Checklist
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I have...
- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed
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- [ ] manually tested (if applicable)
