Fix bugs in the M1 Closure and add tests

[wthrowe]

Fixes:

• Up-down tensor index agreement error
• Assigning to entire DataVectors instead of components

Ping @pajkosmi

Proposed changes

Upgrade instructions

Code review checklist

• The code is documented and the documentation renders correctly. Run
  make doc to generate the documentation locally into BUILD_DIR/docs/html.
  Then open index.html.
• The code follows the stylistic and code quality guidelines listed in the
  code review guide.
• The PR lists upgrade instructions and is labeled bugfix or
  new feature if appropriate.

Further comments

[wthrowe]

@sxs-collaboration/spectre-core-devs Can someone review this? I believe it is blocking @pajkosmi (#6132 in particular).