Update ECR Regex to support new dual stack endpoints + tests

[BDworak]

What type of PR is this?
/kind feature

What this PR does / why we need it:
This PR modifies the ECR Registry Regex to add support to new up and coming ECR Dual Stack endpoints. These endpoints are in the format:

<account_id>.dkr-ecr.<region>.on.aws
<account_id>.dkr-ecr.<region>.on.amazonwebservices.com.cn
<account_id>.dkr-ecr-fips.<region>.on.aws

This PR also cleans up the parseRegionFromECRPrivateHost function to expect 5 capture groups from the ecrPrivateHostPattern regex that would be of interest within the code.
Example input: 123456789123.dkr-ecr-fips.us-west-2.on.aws
Captures:

• 0 -123456789123.dkr-ecr-fips.us-west-2.on.aws (Entire match)
• 1 - 123456789123 (Account ID)
• 2 - -fips (Fips endpoint)
• 3 - us-west-2 (region)
• 4 - on.aws (Domain)

Testing was added for the parseRegionFromECRPrivateHost method to account for all possible combinations of ECR FQDN ensuring accurate parsing of the regex.

Special notes for your reviewer:
CR for support in EKS AMI pending merge - awslabs/amazon-eks-ami#2082

Does this PR introduce a user-facing change?:

NONE

 Add support for Dual Stack ECR endpoints in ecr-credential-provider

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: BDworak / name: Bart Dworak (cef3b8f)

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[cartermckinnon]

/ok-to-test

[kmala]

/lgtm

[cartermckinnon]

/approve

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