--registry-config not working for destination registry in oras cp

[qweeah]

What happened in your environment?

Suppose $REG points to a registry which requires login for both push and pull. When using below commands to copy an image from $REPO1 to $REPO2, the execution will fail with 401

oras login $REG --registry-config config.json
# input username and password, or token
oras cp $REG/$REPO1:v1 $REG/$REPO2:v1 --registry-config config.json
# 401 error

What did you expect to happen?

oras cp should support --from-registry-config and --to-registry-config for source and destination registry.

How can we reproduce it?

# 0. have a registry that requires login for both pull and push
# 1. login $REG and store the cred to config.json
oras login $REG --registry-config config.json

# 2. copy between repositories
oras cp $REG/$REPO1:v1 $REG/$REPO2:v1 --registry-config config.json
# will get 401 error

What is the version of your ORAS CLI?

Version: 1.0.0-rc.1
Go version: go1.19.5
Git commit: a98931b
Git tree state: clean

What is your OS environment?

ubunto 20.04

Are you willing to submit PRs to fix it?

• Yes, I am willing to fix it.