Slow schema documentation tooltip

## Problem

Great to see the unified SAM and CloudFormation schema in the latest release!

I noticed it takes about a second on my computer for the documentation tooltip to show up upon hover:

However, if I use the modeline to manually override with the same schema, it's pretty much instantaneous:

```bash
# yaml-language-server: $schema=https://raw.githubusercontent.com/aws/serverless-application-model/main/samtranslator/schema/schema.json
```

The final visible behavior is identical in both cases.

While in absolute terms it's a small difference, in relative terms it's very noticeable, and hinders the experience of quickly exploring a template ([this NN article](https://www.nngroup.com/articles/response-times-3-important-limits/) is also relevant).

## Steps to reproduce the issue

1. Create a new YAML file with the following contents:

```yaml
Transform: AWS::Serverless-2016-10-31
Resources:
MyTable:
Type: AWS::Serverless::SimpleTable
Properties:
TableName: foo
```
2. Hover over `TableName`. On my computer it takes about a second for the hover tooltip to show up.
3. Now manually override with the same schema by adding the following at the top:

```yaml
# yaml-language-server: $schema=https://raw.githubusercontent.com/aws/serverless-application-model/main/samtranslator/schema/schema.json
```
3. Try hovering over `TableName`. It should be pretty much instantaneous; on my computer it's significantly snappier than before. The tooltip is otherwise exactly the same.

## Expected behavior

Documentation should show up as fast as without AWS Toolkit (i.e. using just the [YAML extension](https://github.com/redhat-developer/vscode-yaml)).

## System details (run the `AWS: About Toolkit` command)

- OS: Darwin x64 22.3.0
- Visual Studio Code extension host: 1.76.2
- AWS Toolkit: 1.65.0
- node: 16.14.2
- electron: 19.1.11

Reproduce the delay with the YAML sample in the issue, then compare AWS Toolkit hover behavior with the same schema supplied through the yaml-language-server modeline. Trace the AWS Toolkit schema integration and measure hover latency; done means documentation appears as quickly as it does without AWS Toolkit while retaining the same tooltip content.

Written by the indexing model from the issue text.