Wrap StatsDimensionsValue over structured parcel

Reduces code complexity by leveraging the readFromParcel and
createFromParcel functions created in the autogenerated
StatsDimensionsValueParcel class.

Wrote a unit test that checks the conversion from a
StatsDimensionsValueParcel to a StatsDimensionsValue.

Test: atest FrameworkStatsdTests
Test: atest GtsStatsdHostTestCases
Bug: 149103391
Change-Id: I64850c6b962a68799d51a26138e95cb1e0c99aee