Add GraphQL name sanitization utilities

[FionaBronwen]

Summary

Adds utility functions for transforming TypeSpec names into valid GraphQL identifiers. These utilities form the foundation for name handling throughout the GraphQL emitter.

Changes

• src/lib/type-utils.ts - Core utility functions for GraphQL name transformations
• test/lib/type-utils.test.ts - Unit tests for sanitizeNameForGraphQL

Utilities Added

Function	Purpose
sanitizeNameForGraphQL	Sanitize names to be valid GraphQL identifiers
toTypeName	Convert to PascalCase for type names
toFieldName	Convert to camelCase for field names
toEnumMemberName	Convert to CONSTANT_CASE for enum members
getUnionName	Generate names for anonymous unions
getTemplatedModelName	Generate names for templated models (e.g., ListOfString)
isArray, isRecordType	Type guards for array/record models
unwrapModel, unwrapType	Extract element types from arrays
isTrueModel	Check if a model should emit as GraphQL object type
getGraphQLDoc	Extract doc comments for GraphQL descriptions

[steverice]

Are we actually using this?

[FionaBronwen]

Yeah it's used to construct Union names and templated model names!