add codespace suffix to quickstart clusters

Adding codespace identifier

## Purpose
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does it solve or functionality does it add? -->
* ...

## Does this introduce a breaking change?
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```
[ ] Yes
[- ] No
```

## Pull Request Type
What kind of change does this Pull Request introduce?

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```
[- ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:
```

## How to Test
*  Get the code

```
git clone [repo-address]
cd [repo-name]
git checkout [branch-name]
npm install
```

* Test the code
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```
```

## What to Check
Verify that the following are valid
* ...

## Other Information
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This is related to this bug - [Telemetry can't distinguish between K3s
on Codespaces (getting started msft infra) vs. K3 on customer
infra](https://msazure.visualstudio.com/One/_workitems/edit/31306566)

---------

Co-authored-by: John Lian <[email protected]>

Author: david-emakenemi

.devcontainer/postStartCommand.sh

@@ -1,5 +1,5 @@
 echo 'export CODESPACES="FALSE"' >> ~/.bashrc
-echo 'export CLUSTER_NAME=${CODESPACE_NAME%-*}' >> ~/.bashrc
+echo 'export CLUSTER_NAME=${CODESPACE_NAME%-*}-codespace' >> ~/.bashrc
 source ~/.bashrc
 
 echo -e "Environment: \nSUBSCRIPTION_ID: $SUBSCRIPTION_ID \nRESOURCE_GROUP: $RESOURCE_GROUP \nLOCATION: $LOCATION \nCLUSTER_NAME: $CLUSTER_NAME"