[CMCD] - Update Custom key pattern to match what spec allows #1028

Use case description

Noticed that the CUSTOM_KEY_NAME_PATTERN regex in CmcdData class is not compliant to spec where it states that "Clients
SHOULD use a reverse-DNS syntax when defining their own prefix" when defining custom CMCD keys. Custom key examples of this syntax in spec, such as com.example-myNumericKey=500, causes errors due to it not matching the pattern. I've personally come across ExoPlaybackException: Unexpected runtime error caused by IllegalStateException at validateCustomDataListFormat method when trying to play some content.

Proposed solution

Update in CmcdData class:

private static final Pattern CUSTOM_KEY_NAME_PATTERN =
    Pattern.compile("^(([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\\-]*[a-zA-Z0-9])\\.)*([A-Za-z0-9])+(-[A-Za-z0-9]+)$");

Validated that this pattern allows reverse-DNS syntax and hyphen is still required.
Valid examples:

• com.example-somekey
• com.example.test-key
• test-key

Alternatives considered

N/A