Fix doctor

[Fatme]

Don't show components info when tns doctor command is executed outside of project directory. Don't print warning twice when tns doctor command is executed and env is not properly configured.

In case when some issues are detected, checkEnvironmentRequirements prints the detected warnings. (actually canExecuteLocalBuilds print them). In case when no issues are found, we need to print them from printWarnings method.

PR Checklist

• The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#commit-messages.
• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
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• All existing tests are passing: https://github.com/NativeScript/nativescript-cli/blob/master/CONTRIBUTING.md#contribute-to-the-code-base
• Tests for the changes are included.

[rosen-vladimirov]

run ci