Add LoRA-FA support

[PeanutButterRat]

Is your feature request related to a problem? Please describe:
LoRA is designed to reduce the memory requirements to finetune LLMs and already exists in Fairseq2 to some capacity. LoRA-FA reduces the memory overhead of vanilla LoRA even further by freezing the A matrix while leaving the B matrix as trainable.

Describe the solution you would like:
Because LoRA-FA is effectively an extension of LoRA, there should be an additional parameter in the LoRAConfig class that is used to effectively enable/disable LoRa-FA.

Describe the alternatives you have considered:
None

Additional Context:
None