Replace occurrences of PCM with PCUI and rename files accordingly

Description

This PR aims to replace occurrences of PCM / PclusterManager / ParallelClusterManager with "ParallelCluster UI" and rename files accordingly.

pcluster-manager.yaml -> parallelcluster-ui.yaml
pcluster-manager-cognito.yaml -> parallecluster-ui-cognito.yaml
In some resources the PclusterManager prefix has been removed since considered not useful. All resources created will still have the stack name as prefix.

[ ] I added tests to new or existing code
[ ] I removed hardcoded strings and used our i18n solution instead (see here)
[ ] I made sure no sensitive info gets logged at any time in the codebase (see here) (e.g. no user info or details, no stacktraces, etc.)
[ ] I checked that infrastructure/update_infrastructure.sh runs without any error
[ ] I checked that npm run build builds without any error
[ ] I checked that clusters are listed correctly
[ ] I checked that a new cluster can be created (config is produced and dry run passes)
[ ] I checked that login and logout work as expected

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