make RAPIDS_AUX_SECRET_1 be an input variable secret name, not the secret itself

[trxcllnt]

Switches the RAPIDS_AUX_SECRET_1 value to an input of a secret name, then defines the RAPIDS_AUX_SECRET_1 envvar from the secrets context to align with the way we're passing in other secrets.

Without this change, it isn't possible for a calling workflow to define both inputs.extra-repo-deploy-key and secrets.RAPIDS_AUX_SECRET_1 -- the caller has to choose either:

1. { secrets: inherit, with: { extra-repo-deploy-key: 'KEY_NAME' } }, or
2. { secrets: { RAPIDS_AUX_SECRET_1: ${{ secrets.SECRET }} } }

In the second case, the shared workflow's secrets context only contains RAPIDS_AUX_SECRET_1, not KEY_NAME, because we had to pass it instead of secrets: inherit.

[trxcllnt]

/merge

[ajschmidt8]

since this is a breaking change, have all of the affected repositories been accounted for and updated accordingly?

[trxcllnt]

Yes they have. The only use is in an inactive private repo that has an open PR to update.