fix: Use wrangler secret put instead of deprecated secret:bulk command

[jahands]

wrangler secret:bulk is deprecated and will be removed in a future version.

This improves logging in cases where a secret is failing to upload because an environment variable with the same name already exists (see: #240). Example:

With this change, we get this:

Testing:

Tested with a repo where the Worker already contains a secret of a different type: https://github.com/jahands/wrangler-action-example/actions/runs/11895527967/job/33145312742

[Maximo-Guk]

We now have some baby tests in wranglerAction.test.ts #322 , so it's possible to write some tests for uploadSecrets() if you're so inclined!

[Cherry]

Yeah, this would be a pretty major behavioural change to revert to the old method of setting individual secrets. Using wrangler secret put for tens of secrets within a worker can result in errors from the API since they're run in parallel and sometimes don't get acknowledged quickly enough and then cause a mismatch, as well as that many individual new deploys of your worker, cluttering up the versions list. Not to mention drastically slow down the deploy time too.

[jahands]

Closing as this was not the right way to fix this. Looking into improving logging in bulk puts