[debug-certificate-manager] - rename extension ID const

[TheLarkInn]

nit: @ext is a setting prefix to look for extension id and not part of the extension id itself. consider renaming the const to SETTINGS_EXTENSION_ID_FILTER or keep the string concatenation in extention.ts

Also, See if you can source this info from the extension manifest to avoid future issues like this. We can also start using that pattern for other vscode extensions here.

import packageJson from '../package.json';
// ....
export const EXTENSION_ID: string = `${packageJson.publisher}.${packageJson.name}`

Originally posted by @bmiddha in #5493 (comment)