Automated release for multiple hdk versions

[harlantwood]

Example Version:
0.3.3-pre+hdk-0.0.122

The +… part is valid semver:
https://semver.org/#spec-item-10

Implementation:

• when ready to release a new version, cut a branch eg:
  release/0.3.4
• push branch to GitHub
• on CI, we detect this new branch (release/x.x.x) and:
• Run tests and checks
• If anything fails, try clearing .cargo and target and try again
• Read the current hdk version in use from cargo.toml (eg 0.0.122)
• Bump version in cargo.toml to 0.3.4-pre+hdk-0.0.122
• Git tag that version number
• Push to GitHub
• Push to crates.io
• Repeat this process for all higher hdk versions that exist (eg 0.0.123, etc)
• Repeat this process for up to 10 hdk versions total, including those lower than the starting hdk version

notes:

• All of this happens on the release/0.3.4 branch
• Only release versions when all checks pass
• Stop trying to go up if a version fails
• Stop trying to go down if a version fails

[harlantwood]

Hopefully not needed now that hdk is stabilizing