Display unit of elevation in met config flow (#88283)

* display unit of elevation in met config flow

Co-authored-by: lijake8 <lijake8@users.noreply.github.com>
Signed-off-by: Chris Xiao <30990835+chrisx8@users.noreply.github.com>

* use NumberSelector for met config flow

* met remove unused is_metric param

---------

Signed-off-by: Chris Xiao <30990835+chrisx8@users.noreply.github.com>
Co-authored-by: lijake8 <lijake8@users.noreply.github.com>