Write Alg data to and read from a file instead of a limited buffer

[lefou]

For context:

For larger projects, the structured dependency information (JSON) overflows the buffer Scala Steward is using, resulting in an exception, but effectively no new dependency updates.

• PRs not being sent in for various projects VirtusLab/scala-steward-repos#98
• Increase default --max-buffer-size #3282

This is a long standing issue hard to solve by tweaking the JSON format alone. Projects like Mill, with a rich set of integration tests integrated in the build resulting in more that 2000 build modules, won't fit the concept.

The easiest alternative would be to use a exchange file instead of a limited buffer.