[SECURITY] Audit the opentelemetry-cpp repository for supply chain attacks

In light of the xz attack:

• https://arstechnica.com/security/2024/04/what-we-know-about-the-xz-utils-backdoor-that-almost-infected-the-world/

audit the opentelemetry-cpp repository for possible attack vectors.

Full list of checks to be determined.

To start with:

• review executable permissions on files
• audit and remove all binary files from the repository (not aware of any)
• enforce CI to forbid binary files
• audit binary downloads used during the build process
• enforce checksums when appropriate
• cutoff unnecessary dependencies when practical
• prefer installing dependencies from the OS distribution, when practical

Subtasks:

• #2627
• CI to forbid binary files