Rename SomeWitness to SomeSigningWitness. Rename constructors to avoid name conflicts.

[newhoggy]

Changelog

- description: |
    Rename `SomeWitness` to `SomeSigningWitness`.  Rename constructors to avoid name conflicts.  Move to `Key` module.
# uncomment types applicable to the change:
  type:
  # - feature        # introduces a new feature
  # - breaking       # the API has changed in a breaking way
  - compatible     # the API has changed but is non-breaking
  # - optimisation   # measurable performance improvements
  - improvement    # QoL changes e.g. refactoring
  # - bugfix         # fixes a defect
  # - test           # fixes/modifies tests
  # - maintenance    # not directly related to the code
  # - release        # related to a new release preparation
  # - documentation  # change in code docs, haddocks...

Context

The word "witness" on its own can be ambiguous because we use that word in the context of proving an operation is valid in an era. To avoid any confusion, rename SomeWitness to SomeSigningWitness.

Furthermore, the constructor names in SomeWitness types conflict with that of SomeSigningKey. Rename those constructors to end with SigningWitness instead of SigningKey to deconflict.

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• The change log section in the PR description has been filled in
• New tests are added if needed and existing tests are updated. These may include:
  • golden tests
  • property tests
  • round trip tests
  • integration tests
    See Running tests for more details
• The version bounds in .cabal files are updated
• CI passes. See note on CI. The following CI checks are required:
  • Code is linted with hlint. See .github/workflows/check-hlint.yml to get the hlint version
  • Code is formatted with stylish-haskell. See .github/workflows/stylish-haskell.yml to get the stylish-haskell version
  • Code builds on Linux, MacOS and Windows for ghc-8.10.7 and ghc-9.2.7
• The changelog section in the PR is updated to describe the change
• Self-reviewed the diff