Query free space remaining in allocation before attempting an upload

[stewartie4]

When attempting to upload a file larger than the allocation allows, the file is first uploaded to the blobber, then the blobber returns an error if it is too large.
This is problematic for 2 reasons:

1. It is very wasteful and time consuming for both the client and server
2. There is a possible DOS attack vector where a giant file is uploaded to blobber temp storage even though the allocation does not allow it
3. Sometimes (inconsistently) a panic occurs:
   ERROR extgen/config.go:201 Encountered a panic {"recovered": "runtime error: index out of range [1024] with length 1024"}
   main.(*PhaseGoal).SpawnWorkers.func3.1.1.1
   /go-external-txn-generator/go/0chain.net/txngen/extgen/config.go:201
   runtime.gopanic
   /usr/local/go/src/runtime/panic.go:965
   runtime.goPanicIndex
   /usr/local/go/src/runtime/panic.go:88
   github.com/0chain/gosdk/core/util.(*FixedMerkleTree).Write
   /go/pkg/mod/github.com/0chain/[email protected]/core/util/fixed_merkle_tree.go:52

Acceptance criteria:
First query the allocation free space and reject the upload on the client side if the file is too large