Fix an issue with editorconfig tab_size

[Colengms]

Fixes an issue with .editorconfig tab_size not being applied to VS Code's tab size when in "space" (soft tab) mode.

I ran into this with the EDG codebase. (host_envir.c/.h are much easier to look at now).

The new check seems simpler:

• First, indent_style is applied, only if present, to VS Code's insertSpaces option.
• Independently of that, indent_size is applied to VS Code's indentSize AND tabSize (as a fallback/default).
  • Or, if it's the special value tab, VS Code's indentSize option is set to its own special value of tabSize (telling VS Code to use the value of tabSize instead).
• Then, also independent of the other two options, if tab_width is specified, it's applied to VS Code's tabSize option.

Based on information here:

• https://editorconfig.org
• https://github.com/microsoft/vscode/blob/92fb591f1b8f26539a80c5269fa6fb6f0b9499ee/src/vscode-dts/vscode.d.ts#L672-L696

[fearthecowboy]

Looks good to me