Remove clearAll from LoadInitialState to fix cluster deep link not selecting the cluster

[tmscarla]

Description

Currently when loading PCUI with a deep link pointing to a specific cluster (e.g. /clusters/{:clusterName}), the cluster in the deep link does not get selected.

Steps to reproduce:

1. select a cluster and refresh the page
2. see that no cluster gets selected

This PR aims at solving this issue by extracting the clearAllState out of the LoadInitialState function and call it directly in the region selection callback, since its purpose is to clear the state when LoadInitialState is called when changing the region.

Closes #30.

How Has This Been Tested?

1. Selected a cluster
2. Refreshed page
3. Verified that cluster is still selected

PR Quality Checklist

• I added tests to new or existing code
• I removed hardcoded strings and used react-i18next library (useTranslation hook and/or Trans component), see an example 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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