feat: Transfer Manager ParallelCompositeUploads

[sydney-munro]

This implements ParallelCompositeUploads(PCU) in Transfer Manager.

ParallelCompositeUpload in Transfer Manager is an opt-in feature, customers will have to update their config to allow Transfer Manager to perform PCU operations on their behalf. Transfer Manager will only do this if the following conditions are met:

• The customer has set allowParallelCompositeUpload to true
• The file to be uploaded is 4 * the buffer per worker size
• The customer has specified enough threads that ParallelCompositeUpload can be of benefit while still cuing other work.

[BenWhitehead]

One cleanup item related to options.

Can you also purge out the owlbot commit, it's adding noise to the PR unrelated to your change.