Create matrix for fuzzing

[Alan-Jowett]

This pull request includes changes to the .github/workflows/fuzzing.yml file, which is part of the GitHub Actions workflow. The changes primarily focus on replacing the use of environment variables with a matrix strategy for the job configurations. This allows for more flexibility in defining and managing the job configurations.

Here are the most important changes:

• Replaced the env: block with a strategy: block that uses a matrix to define platform and arch parameters. This change allows for more flexibility in defining and managing the job configurations.

• Updated the runs-on: field to use the matrix.platform value instead of the env.platform value. This change is in line with the switch to a matrix strategy.

• Updated the run: field in the "Generate the cache key" step to use the matrix.platform and matrix.arch values instead of the env.platform and env.arch values. This change ensures that the cache key is generated correctly based on the matrix values.

• Updated the if: conditions in various steps to use the matrix.platform value instead of the env.platform value. This change ensures that the correct steps are executed based on the platform defined in the matrix. [1] [2]

• Removed the scan_build environment variable and the corresponding conditional logic. This simplifies the workflow as the scan_build variable was not being used elsewhere.

• Changed the DCMAKE_BUILD_TYPE value from a variable (env.build_type) to a fixed string ("Debug"). This change simplifies the workflow and ensures that the build type is always "Debug" for this job.