Fix schema priority lookup for normalized file URIs

[shin19991207]

What does this PR do?

Before the fix, schema registration normalizes URIs to skip encodings, however, schema priorities were stored using the original URI. For an encoded Windows file URI, this produced different keys:

Priority key:  file:///c%3A/Users/.../schema.json
Registered ID: file:///c:/Users/.../schema.json

As a result, the configured schema's priority could not be found and defaulted to 0. Another matching schema could then incorrectly take precedence over the schema configured through yaml.schemas.

This PR normalizes URIs consistently when recording schema priorities, ensuring encoded and unencoded forms of the same URI use the same key.

What issues does this PR fix or reference?

Related to redhat-developer/vscode-yaml#1274

Is it tested? How?

• New automated tests
• Tested manually on Mac using the following setting:

  "yaml.schemas": {
      "file:///Users/.../encoded%3Aschema.json": "test.yaml",
      "file:///Users/.../schema.json": "test.yaml"
  }

  Expected test.yaml to be validated against Multiple JSON Schemas (both encoded:schema.json and schema.json), instead of just schema.json.

[datho7561]

I confirmed that overriding the schema with an encoded colon causes it to not be used when there's two schemas assgined to a file, and that this fixes that.

I'll play around with it on Windows too to see if I can replicate that problem and if this fixes it. Do you want to merge this as-is, or wait to hear back from phaumer?

[shin19991207]

@datho7561 I think this PR can be merged as-is. I'll open another PR for the original reported issue when we can actually reproduce and identify the issue.

[datho7561]

Sounds good, let's merge, then