aml_tester: Add positional file arguments, in-order parsing and shared namespace

[rw-vanc]

• --path DIR or positionals FILE... must be specified, but not both. Only one DIR is accepted at this time
• namespace is shared between tables by default, --reset to have a fresh namespace for each table
• files are processed in the order they are listed in the command line or directory, if an aml file and its asl source both appear in the list, the first occurrence will be taken as the intended sequence, repeated instances are ignored
• if iasl is missing, it is only reported after checking if anything needs to be compiled

[IsaacWoods]

Thanks - apologies this has sat for so long, all look like good changes. I think CI will need adjusting after this merges, so I'll do that straight into main.