[Bicep CLI] Add linter as a sub-command

[rchaganti]

Is your feature request related to a problem? Please describe.
Bicep CLI is invoking linter at the time of build and the errors/warnings are shown in the output. When the intention is not to build an ARM JSON template but only to get the linter output, it will be beneficial to have linting as a sub-command.

Describe the solution you'd like
Something like bicep --lint main.bicep could be helpful in a CI / CD as a separate step.

[alex-frankel]

Dup of #2811