chore: remove @metamask/chain-controller (#5137)

## Explanation

This controller has never been really used. Initially it was added to
work in pair with this repository:
- https://github.com/MetaMask/accounts-chain-api/

But this Chain API has been revamped and has finally been merged with
the existing Keyring API with the addition of the `getAccountBalances`
method which replaces this `getBalances` method from the Chain API.

## References

N/A

## Changelog

N/A

## Checklist

- [ ] I've updated the test suite for new or updated code as appropriate
- [ ] I've updated documentation (JSDoc, Markdown, etc.) for new or
updated code as appropriate
- [ ] I've highlighted breaking changes using the "BREAKING" category
above as appropriate
- [ ] I've prepared draft pull requests for clients and consumer
packages to resolve any breaking changes

.github/CODEOWNERS

@@ -9,7 +9,6 @@
 ## Accounts Team
 /packages/accounts-controller        @MetaMask/accounts-engineers
 /packages/keyring-controller         @MetaMask/accounts-engineers
-/packages/chain-controller           @MetaMask/accounts-engineers
 
 ## Assets Team
 /packages/assets-controllers         @MetaMask/metamask-assets
@@ -71,8 +70,6 @@
 /packages/approval-controller/CHANGELOG.md        @MetaMask/confirmations @MetaMask/wallet-framework-engineers
 /packages/assets-controllers/package.json         @MetaMask/metamask-assets @MetaMask/wallet-framework-engineers
 /packages/assets-controllers/CHANGELOG.md         @MetaMask/metamask-assets @MetaMask/wallet-framework-engineers
-/packages/chain-controller/package.json           @MetaMask/accounts-engineers @MetaMask/wallet-framework-engineers
-/packages/chain-controller/CHANGELOG.md           @MetaMask/accounts-engineers @MetaMask/wallet-framework-engineers
 /packages/ens-controller/package.json             @MetaMask/confirmations @MetaMask/wallet-framework-engineers
 /packages/ens-controller/CHANGELOG.md             @MetaMask/confirmations @MetaMask/wallet-framework-engineers
 /packages/gas-fee-controller/package.json         @MetaMask/confirmations @MetaMask/wallet-framework-engineers

README.md

@@ -27,7 +27,6 @@ Each package in this repository has its own README where you can find installati
 - [`@metamask/assets-controllers`](packages/assets-controllers)
 - [`@metamask/base-controller`](packages/base-controller)
 - [`@metamask/build-utils`](packages/build-utils)
-- [`@metamask/chain-controller`](packages/chain-controller)
 - [`@metamask/composable-controller`](packages/composable-controller)
 - [`@metamask/controller-utils`](packages/controller-utils)
 - [`@metamask/ens-controller`](packages/ens-controller)
@@ -70,7 +69,6 @@ linkStyle default opacity:0.5
   assets_controllers(["@metamask/assets-controllers"]);
   base_controller(["@metamask/base-controller"]);
   build_utils(["@metamask/build-utils"]);
-  chain_controller(["@metamask/chain-controller"]);
   composable_controller(["@metamask/composable-controller"]);
   controller_utils(["@metamask/controller-utils"]);
   ens_controller(["@metamask/ens-controller"]);
@@ -112,7 +110,6 @@ linkStyle default opacity:0.5
   assets_controllers --> network_controller;
   assets_controllers --> preferences_controller;
   base_controller --> json_rpc_engine;
-  chain_controller --> base_controller;
   composable_controller --> base_controller;
   composable_controller --> json_rpc_engine;
   ens_controller --> base_controller;