Append Tensor to FactorSharding struct name.

[copybara-service]

Append Tensor to FactorSharding struct name.

FactorSharding has isMinorMost field which depends on the tensor, while the other fields, axisRef, overflowAxes, and isClosed can be shared among the tensors.

Hence TensorFactorSharding defines a tensor-depending factor sharding. The target, by a subsequent change, is to get the following structured:

TensorFactorSharding {
FactorSharding factorSharding,
bool isMinorMost
}

FactorSharding {
SmallVector axisRefs,
bool isClosed,
SmallVector overflowAxes
}

One motivation is ShardingProjection::build from common factor shardings, where the isMinorMost needs to be tensor specific and should be determined by the sharding rule, not from the common factor sharding.