token-cli: Use the commitment field from Solana config

[acheroncrypto]

Problem

spl-token CLI doesn't respect the commitment field of Solana config when creating the RPC client.

See #7590 for more details.

Summary of changes

Use the confirmation field from the Solana config when creating the RPC client.

Note: This won't affect any users (unless they've overridden the commitment field) because confirmed is already the default commitment of Solana config.

Resolves #7590

[joncinque]

Thanks for noticing and fixing this! Since the token-cli doesn't accept a commitment parameter otherwise, it makes sense to just read whatever is in the config file.

And if there's an invalid commitment in the config file, then the base Solana CLI falls back to confirmed, so this change is totally consistent with the base CLI.