introduce QA pipeline for protobuf schemas

[jkowalleck]

current protobuf schema files are not perfect.

this PR aims to prevent mistakes in the future, while acknowledging issues from the past.

fixes #384

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status

• [x] introduce protobuf QA tools and configure them to our needs
• [x] baseline existing protobuf QA violations - as acknowledgement
• [x] introduce the protobuf QA tools in automated pipeline
• [x] introduce tools that detect and prevent breaking changes (BCD) in protobuf
• [x] introduce the protobuf BCD tools in automated pipeline
• [x] have our own protobuf test files checked against the schemas

followup

• [x] add the appropriate header to *.textproto
  see also: https://github.com/CycloneDX/specification/issues/384#issuecomment-1959512503 --> https://github.com/CycloneDX/specification/issues/392
• [x] create ticket for BC: fix the proto3 schema enum value 0 -- they are intended to be fallbacks, not actual values. -> https://github.com/CycloneDX/specification/issues/391

[jkowalleck]

The schema linting and breaking-changes detection is in place.

@nscuro, could you do a review?

[jkowalleck]

this is how a positive run report looks like : https://github.com/CycloneDX/specification/actions/runs/8081208041/job/22079240901

this is how a negative PR/run would look like: https://github.com/CycloneDX/specification/pull/388

• see annotation in file around line 1791 -> https://github.com/CycloneDX/specification/pull/388/files#diff-31a634760e9b4432c392ead00601567422a8cc12ac462dead1a7f7ab9fa90fdbR1791
• see run res: https://github.com/CycloneDX/specification/actions/runs/8019818776/job/21908366440#step:3:31