feat: Make group module a standalone go module (#10059)

## Description

Make group module a standalone go module which will allow us to have a smaller release team.

Closes: #9896 
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---

### Author Checklist

*All items are required. Please add a note to the item if the item is not applicable and
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/master/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/master/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/master/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)

x/group/go.mod

@@ -0,0 +1,17 @@
+go 1.15
+
+module github.com/cosmos/cosmos-sdk/x/group
+
+require (
+	github.com/cosmos/cosmos-sdk v0.43.0
+	github.com/gogo/protobuf v1.3.3
+	github.com/regen-network/cosmos-proto v0.3.1
+	google.golang.org/grpc v1.40.0
+	google.golang.org/protobuf v1.27.1
+)
+
+replace google.golang.org/grpc => google.golang.org/grpc v1.33.2
+
+replace github.com/gogo/protobuf => github.com/regen-network/protobuf v1.3.3-alpha.regen.1
+
+replace github.com/cosmos/cosmos-sdk => ../../