Migrate away from release-please

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release-please is this particularly annoying tool that does a middling job of solving a very hairy, un-fun problem: version management within complex workspaces of inter-related packages. Unfortunately, it's current status is best described as neglected (though still technically maintained), it's extremely janky and has slowed us down a number of times in the past. And even more unfortunately, there are no good alternatives that cover all the same surface area; without release-please, we would be even slower.

This issue is a placeholder while we scheme desperately to arrive at an alternative workflow for releases.

Running list of problems we have with it:

• Are Rust workspaces in sub-directories supported? googleapis/release-please#1724
• cargo-workspace plugin ignores changes in workspace.dependencies googleapis/release-please#1896
• Release workflow incorrectly overwrites existing release binaries #615
• cargo-workspace plugin cannot handle dependency cycles in dev-dependencies googleapis/release-please#1662 (comment)