[SAI-5330] Set the default value of priorityBasedEnabled to false

[hiteshk25]

SAI-5330 Fixed the null pointer exception by setting the default value. (it happens when you don't set priorityBasedEnabled)

[patsonluk]

Just several thoughts:

1. Looks like these changes are in 9_7 only, are we going to merge them to 9.x later? cause usually we start with 9x first and cherry pick to 9_7 (tho i do see some existing changes on RateLimiterPayload are in 9_7 only it seems)
2. For consistencies, perhaps we need null check for field enabled at here as well otherwise it will throw NPE if not defined. As the @JsonProperty definition of enabled was not marked as required, and the doc implies that it is not required - since there's a default (as false).
3. This one is kinda minor, but other fields appear to not define the default values in the bean itself (RateLimiterPayload) but at the actual usage of the field. The RateLimiterPayload seems to be a pure bean that makes no assumption of default values (as in other fields). That being said, setting a default in RateLimiterPayload is likely not a big deal 🤷🏼 (subtle difference in the copy and equals method, it could in some scenario write a false value back to the json if it was undefined?)

[hiteshk25]

1. Good catch. I will merge all these change in branch_9x.
2. Updated. I saw it but didn't want to change other code.
3. Bean thing is weird(null vs default value). But now equal/copy should be ok. Those are mainly used for dynamic change. whether config is changed or not.