Support prototype doc's path relative to the running script

[maximpn]

Epic: #200312

Summary

Make prototype document relative path resolved against consumer script's path. Current directory shouldn't be used to resolve prototype document relative path .

Details

OpenAPI bundler kbn-openapi-bundler supports an external prototype document. It provides a way to declare OpenAPI informational properties like info and tags in a separate YAML file and provides better DX than editing that data in a JS file.

Currently bundler resolves prototype document's relative path against current directory. It makes it inconvenient to use external prototype documents.

Prototype document's path should be resolved based on the consumer script's path.