fix(network-enablement-controller): enable Bitcoin networks if enabled in MultichainNetworkController (#6455)

## Explanation

Bitcoin networks are not enabled by default in the Network Enablement
Controller, causing the `enabledNetworks` object to show Bitcoin as an
empty namespace (`"bip122": {}`) instead of showing Bitcoin mainnet as
enabled. This is inconsistent with how Solana networks are handled. This
discrepancy is cashing a crash in Flask builds

This change makes Bitcoin networks follow the same enablement pattern as
Solana networks:

1. Default state: Bitcoin mainnet is now enabled by default in Flask
builds alongside Ethereum and Solana
2. Initialization: The `init()` method enables Bitcoin mainnet if it
exists in MultichainNetworkController configurations
3. Popular networks: The enableAllPopularNetworks() method now includes
Bitcoin mainnet enablement

## References

Fixes [#12345](MetaMask/metamask-mobile#19201)

## 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 communicated my changes to consumers by [updating changelogs
for packages I've
changed](https://github.com/MetaMask/core/tree/main/docs/contributing.md#updating-changelogs),
highlighting breaking changes as necessary
- [x] I've prepared draft pull requests for clients and consumer
packages to resolve any breaking changes

Author: vinnyhoward

packages/network-enablement-controller/CHANGELOG.md

@@ -7,6 +7,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Add Bitcoin network support with automatic enablement when configured in MultichainNetworkController ([#6455](https://github.com/MetaMask/core/pull/6455))
+- Add `BtcScope` enum for Bitcoin mainnet and testnet caip chain IDs ([#6455](https://github.com/MetaMask/core/pull/6455))
+- Add Bitcoin network enablement logic to `init()` and `enableAllPopularNetworks()` methods ([#6455](https://github.com/MetaMask/core/pull/6455))
+
 ### Changed
 
 - Bump `@metamask/base-controller` from `^8.2.0` to `^8.3.0` ([#6465](https://github.com/MetaMask/core/pull/6465))