feat: introduce debug mode

This MR adds the extension setting gitlab.debug. When set to true, the extension resolves stack traces using source maps and it will show debug logs.

The motivation for this MR was this comment: #580 (comment 956134944) I knew that Vim extension enables source map support and I was asking @lhsilveira.ilia to install Vim extension so I see a proper stack trace instead of at methodName (gitlab-vscode-extension/out/extension.js:26681:9)

Without debug mode:

[error]: error
         Error: error
         	at removeAccount (/Users/tomas/workspace/gitlab-vscode-extension/out/extension.js:26681:9)
         	at /Users/tomas/workspace/gitlab-vscode-extension/out/extension.js:29958:11
         	at o._executeContributedCommand (/Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:83:62411)
         	at o.$executeContributedCommand (/Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:83:63115)

With debug mode:

[error]: error
         Error: error
             at removeAccount (/Users/tomas/workspace/gitlab-vscode-extension/src/token_input.ts:43:9)
             at /Users/tomas/workspace/gitlab-vscode-extension/src/extension.ts:69:13
             at o._executeContributedCommand (/Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:83:62411)
             at o.$executeContributedCommand (/Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:83:63115)

[debug]: Using non-expired account {"instanceUrl":"https://gitlab.com","id":"https://gitlab.com|xxx","type":"oauth","username":"viktomas","scopes":["api","read_user"],"token":"xxx","refreshToken":"xxx","expiresAtTimestampInSeconds":1653994614}