## Description
### Issue
Some values (like chain ID) were being leaked from the previous block/initialization into PrepareProposal and ProcessProposal, these values are only available if:
1. The node has never been stopped since the genesis block (as these values are set on `InitChain`)
2. The node has already commited a block (as the previous header was being used for the new state of prepare and process proposal).
So if a node is restarted, during the first prepare and process proposal these values won't be populated, and that will cause issues if they are being used.
### Solution
Remove any previous header information from a previous block in the prepare and process proposal contexts, making things consistent at every height.
- Added ChainID to baseapp
- Use an empty header in Commit() with only the chain id set
- Fix context for prepare and process proposal
Closes: #15269
---
### Author Checklist
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please add links to any relevant follow up issues.*
I have...
- [ ] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [ ] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/main/CONTRIBUTING.md#pr-targeting))
- [ ] provided a link to the relevant issue or specification
- [ ] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/main/docs/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/main/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
- [ ] reviewed "Files changed" and left comments if necessary
- [ ] confirmed all CI checks have passed
### Reviewers Checklist
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your handle next to the items reviewed if you only reviewed selected items.*
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
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)
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