Module update

Self-updates for nextest.

Structs

• MuktiBackend
  Update backend using mukti
• MuktiUpdateContext
  Context for an update.
• NextestReleaseMetadata
  Nextest-specific release metadata.
• NextestReleases
  Release info for nextest.
• ReleaseVersionData
  Like mukti-metadata’s ReleaseVersionData, except with parsed metadata.

Enums

• CheckStatus
  The result of NextestReleases::check.
• UpdateVersion
  Represents the version this project is being updated to.