Improve sanitisation of paths and project names

[f-f]

Fix #1348 - we now properly escape paths when writing the Node script for spago run/spago test.

While writing tests for this I noticed that we were not properly sanitising folder names to use as package names when running spago init, so I bundled that in here since it's a related fix.

[thomashoneyman]

Test failure for windows:

✓ Build succeeded.

Running tests for package: docs-search-index
node:internal/url:827
      href = bindingUrl.parse(input, base, true);
                        ^
TypeError: Invalid URL
    at new URL (node:internal/url:827:25)
    at fileURLToPath (node:internal/url:1608:12)
    at defaultResolve (node:internal/modules/esm/resolve:995:21)
    at #cachedDefaultResolve (node:internal/modules/esm/loader:731:20)
    at ModuleLoader.resolve (node:internal/modules/esm/loader:708:38)
    at ModuleLoader.getModuleJobForImport (node:internal/modules/esm/loader:310:38)
    at ModuleJob._link (node:internal/modules/esm/module_job:182:49) {
  code: 'ERR_INVALID_URL',
  input: 'file://D%3A/a/spago/spago/output/Test.Docs.Search.Main/index.js'
}

Node.js v22.22.0

[f-f]

Right, it's always Windows 😄 I have added a fix for that and added a set of unit tests for the new path encoding logic

[thomashoneyman]

Now it’s Ubuntu!

[f-f]

@thomashoneyman good for a look now 🙂