refactor: ban TypeScript enums across internal-snaps

[ulissesferreira]

Summary

Convert all locally-declared enum and const enum declarations to as const objects with derived union types (Pattern A), and add an ESLint rule banning new enums.

Refs: MetaMask/utils#280, MetaMask/eslint-config#417

Changes

Packages affected

• bitcoin-wallet-snap: 10 enums converted
• solana-wallet-snap: 16 enums converted
• tron-wallet-snap: 11 enums converted
• stellar-wallet-snap: converted (deferred, partially applied — not yet complete)

What changed

• All locally-declared TypeScript enums converted to as const objects + derived union types
• ESLint no-restricted-syntax rule added to ban TSEnumDeclaration
• Type fixes for template literal types, namespace usage patterns, and Array.includes() typing
• Changelogs added for bitcoin, solana, and tron packages

Breaking changes

• Type signatures change: Enum is now a union of string/number literals instead of a nominal enum type
• typeof Enum.Member in type positions now refers to literal values instead of enum member types
• Runtime values unchanged: Member access (Enum.Member) works the same way

Not included

• Stellar package is incomplete — has half-applied fixes, needs full completion before merge
• Unit tests require built bundles (pre-existing infrastructure requirement)
• External/imported enums (from @metamask/utils, @metamask/keyring-api, etc.) are untouched

Validation

• ✅ Per-package tsc --noEmit passes (only pre-existing baseline errors remain)
• ✅ ESLint clean on all changed files
• ✅ oxfmt formatting verified
• ✅ Zero enum declarations remaining in packages/
• ⚠️ Unit tests skipped (require dist/bundle.js build — pre-existing requirement)