github: README: Update code quality analysis

github: README: Update code quality analysis

LGTM code quality analysis is deprecated [1] and no longer generates
code quality information.  Remove the LGTM badge and replace it with
a CodeQL badge.  To facilitate this, move the CodeQL workflow into its
own workflow so that its status can be reported separately from the
automated tests.

[1] https://github.blog/2022-08-15-the-next-step-for-lgtm-com-github-code-scanning/

Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>
Reviewed-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>