## Description
This PR adds benchmarks for inserting, updating, deleting and getting a simple entity compared with handwritten versions of this code.
Two simple optimizations were found with these benchmarks and included in this PR:
* correctly compute buffer size in `KeyCodec.EncodeKey` to avoid growing the buffer
* use `value.String()` instead of `value.Interface().(string)` as the latter causes an additional allocation
Other potential places for optimization can be seen by running CPU and memory profiles. In particular, update is significantly slower because the ORM assumes the existing value always needs to be decoded to keep indexes up-to-date which is not the case in this simple example. In the future, the ORM code generator could potentially generate more code up to the point of essentially mimicking the manual versions if performance tradeoffs become the bottleneck.
As a follow-up, we should do benchmarks using an IAVL tree as the backing store to see if the ORM overhead is significant in a more real-world scenario.
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### Author Checklist
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- [ ] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
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- [ ] added a changelog entry to `CHANGELOG.md`
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