spin new: match unrecognised template as tag

[itowlson]

This, prompted by #1525, makes spin new/add more forgiving of users unsure of the exact template name. If the template is not recognised, it tries to recover by searching for it as a tag:

ivan@hecate:~/testing$ spin new rust tplmadness
Pick a template to start your application with:
> http-rust (HTTP request handler using Rust)
  redis-rust (Redis message handler using Rust)

ivan@hecate:~/testing$ spin new http tplmadness
Pick a template to start your application with:
> http-c (HTTP request handler using C and the Zig toolchain)
  http-empty (HTTP application with no components)
  http-go (HTTP request handler using (Tiny)Go)
  http-grain (HTTP request handler using Grain)
  http-php (HTTP request handler using PHP)
  http-py (HTTP request handler using Python)
  http-rust (HTTP request handler using Rust)
  http-swift (HTTP request handler using SwiftWasm)
  http-zig (HTTP request handler using Zig)
  static-fileserver (Serves static files from an asset directory)

ivan@hecate:~/testing$ spin new biscuits tplmadness
Error: No templates matched 'biscuits'

This could be made even more forgiving by using a name match too:

ivan@hecate:~/testing$ spin new r tplmadness
Error: No templates matched 'r'  # What if this listed all templates containing 'r', or with 'r' in a start-of-word position?

And if we wanted to meet the original request in #1525 we could recognise a special value such as . as matching anything, but then maybe we get into the "I can never remember the special value" problem...

[rylev]

seems reasonable to me!

[rylev]

nit: if there are many tags wouldn't this output look strange (e.g., "foo and bar and baz and qux")?

[itowlson]

The multi-tag case can only happen when the user explicitly supplies tags using the --tag flag. So I can condense this down to No templates matched all tags without listing them. Thanks!