feat: tket2 cli

[ss2165]

TKET2 compilation should have a CLI. We already have some ad-hoc executables, but it is useful to think about a unified interface. Here are some ideas:

• The command should be tket
• The default interface should be something like tket file.hugr -o out.hugr, c.f. llvm-opt. This encourages saving serialized hugr to file so it is worth waiting until we can version that and keep it relatively stable.
• It may be worth having subcommands for more complicated operations (linking hugrs?)

[aborgna-q]

Maybe have sub-commands from the start, so we can e.g. include tket compile, tket taso, etc. ?
Those have different sets of arguments, so having a --taso flag would be impractical.