feat(stepfunctions): Add a setting to opt out of WFS + minor changes

[witness-me]

Problem

1. The feature opens specific file types in a custom editor by default and customers don't have a way to optout while still using toolkit
2. Currently the indentation setting used in the integration defaults to 4 spaces. If it's different in user's VSCode setting, the spacing for the string sent from the integration will not match
3. Currently context menu lacks the command to launch WFS. It has been added before, but it looks it was accidentally added to auto-generated file and was thus removed later

Solution

1. Adding a setting to opt out of WFS, which will close custom editor and open default editor instead. Note that I did not find a way to completely prevent custom editor panel mount - it looks it's not possible, so it will start mounting first and then (in resolveCustomTextEditor) it needs to be witched to default editor. Please advise if that's not the case and the custom editor mount can be prevented earlier (while keeping file format association with the file types)
2. Passing a user setting for tab spacing to be used on the webview side to format JSON/YAML with the right indentation
3. Adding an option to launch WFS from context menu, as it was added before (but this time in the right package.json)

---

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• Your code changes must meet the guidelines in CONTRIBUTING.md.
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[github-actions]

• This pull request modifies code in src/* but no tests were added/updated.
  • Confirm whether tests should be added or ensure the PR description explains why tests are not required.
• This pull request implements a feat or fix, so it must include a changelog entry (unless the fix is for an unreleased feature). Review the changelog guidelines.
  • Note: beta or "experiment" features that have active users should announce fixes in the changelog.
  • If this is not a feature or fix, use an appropriate type from the title guidelines. For example, telemetry-only changes should use the telemetry type.

[justinmk3]

Why is this setting being added?

[witness-me]

This is explained in point 1:

The feature opens specific file types in a custom editor by default and customers don't have a way to optout while still using toolkit

Our team (including the UX) decided that since custom editor is opened by default, we want to provide a way for the user to opt out of it

[justinmk3]

Why is a setting being added? Not explained in the PR description. Looks like a low-value setting. Settings should not be added unless there is a strong use-case.

[justinmk3]

Use workbench.editorAssociations. We already do something similar for threat composer:

aws-toolkit-vscode/packages/toolkit/package.json

Lines 4412 to 4415 in 30face9

	"configurationDefaults": {
	"workbench.editorAssociations": {
	"{git,gitlens,conflictResolution,vscode-local-history}:/**/*.tc.json": "default"
	}

Do not add new, custom ways of setting file associations.

[witness-me]

After discussing offline, we agreed to not add that as a setting, as this is something that can be done with local config file. I'll cancel this PR since that change was its main content, and will publish other small changes in a separate PR