chore(docs): Generate basic OpenAPI specification

[javirln]

This patch introduces several changes that enable the generation of OpenAPI specifications for selected services defined within Chainloop.

Key updates include:

• Corrects the malformed buf.lock file, resolving failures encountered during buf dep update.
• Removed deprecated GitHub action related to buf that unifies all actions into one.
• Adds a generic openapi_metadata.proto file containing common specification information.
• Annotates the ReferrerService and its dependent messages to expose their REST API specifications.
• Updates the make api command to generate the OpenAPI specification, convert it from Swagger 2.0 to OpenAPI 3.0.1, and handle the resulting files.
• Introduces a generic openapi-extra.yaml file, which includes definitions of API endpoints that are not covered by the proto service. The case of the DownloadService.
• Introduces a shell script that adjusts the generated security schema, enabling proper execution of the OpenAPI specification in playground environments. This is necessary because Swagger 2.0 lacks support for the Bearer security type, which would otherwise prevent requests from functioning correctly.
• Formats all proto files running buf format -w.

[jiparis]

Nice job!