moving json-rpc-middleware-stream from merged-packages to actual pack… (#1762)

## Explanation

We chose to place json-rpc-middleware-stream initially in the
merged-packages and not packages so we can hide it from Yarn, ESLint,
Prettier, and TypeScript. In this PR, we cleaned it up and moved it from
`merged-packages` to actual `packages` folder.

In this process, we followed below steps.
Moving to packages
1. Move migration target from merged-packages/ to packages/.
2. Run yarn install in the root directory.
3. Check that all tests are passing in migration target by running `yarn
workspace @metamask/json-rpc-middleware-stream test`.

Lints and Constraints
1. Fixed `yarn lint` errors
2. Fixed `yarn constraints` errors
3. Applied `yarn workspace @metamask/json-rpc-middleware-stream
changelog:validate`

## References

- Closes #1920 

## Changelog Updates

### `@metamask/json-rpc-middleware-stream`

- **BREAKING:** Rename package from `json-rpc-middleware-stream` to
`@metamask/json-rpc-middleware-stream`

## Checklist

- [x] I've updated the test suite for new or updated code as appropriate
- [x] I've updated documentation (JSDoc, Markdown, etc.) for new or
updated code as appropriate
- [x] I've highlighted breaking changes using the "BREAKING" category
above as appropriate

---------

Co-authored-by: Elliot Winkler <[email protected]>
Co-authored-by: Jongsun Suh <[email protected]>
Co-authored-by: Jongsun Suh <[email protected]>

Author: 3 people

constraints.pro

@@ -211,12 +211,14 @@ gen_enforced_field(WorkspaceCwd, 'repository.url', RepoUrl) :-
 gen_enforced_field(WorkspaceCwd, 'license', 'MIT') :-
   \+ workspace_field(WorkspaceCwd, 'private', true),
   WorkspaceCwd \= 'packages/json-rpc-engine',
+  WorkspaceCwd \= 'packages/json-rpc-middleware-stream',
   WorkspaceCwd \= 'packages/eth-json-rpc-provider'.
 % The following published packages use an ISC license instead of MIT.
 gen_enforced_field(WorkspaceCwd, 'license', 'ISC') :-
   \+ workspace_field(WorkspaceCwd, 'private', true),
   (
     WorkspaceCwd == 'packages/json-rpc-engine' ;
+    WorkspaceCwd == 'packages/json-rpc-middleware-stream' ;
     WorkspaceCwd == 'packages/eth-json-rpc-provider'
   ).
 % Non-published packages do not have a license.