refactor(ecocredit/marketplace): BuyDirect (#967)

* refactor: separate buy and buy direct

* chore: slim down test

* fix: comment

* chore: cleanup

* chore: add decimal test case'

* chore: make tidy

* chore: remove print

* chore: Int64() -> String()

* chore: apply suggestions from code review

Co-authored-by: Ryan Christoffersen <12519942+ryanchristo@users.noreply.github.com>

* fix: import order

* chore: make buy fail in validate basic

* chore: proto-gen

* chore: add comment explaining div by 1

* refactor: price per credit -> bidprice

* refactor: add orderOptions struct

* refactor: batch direct buy orders

* chore: address review

* chore: remove buy.go

* refactor: string -> big int

* chore: remove all buy code

* Update x/ecocredit/server/marketplace/buy_direct.go

Co-authored-by: Ryan Christoffersen <12519942+ryanchristo@users.noreply.github.com>

* Update x/ecocredit/server/marketplace/buy_direct.go

Co-authored-by: Ryan Christoffersen <12519942+ryanchristo@users.noreply.github.com>

* Update x/ecocredit/server/marketplace/utils.go

Co-authored-by: Ryan Christoffersen <12519942+ryanchristo@users.noreply.github.com>

* Update x/ecocredit/server/marketplace/utils.go

Co-authored-by: Ryan Christoffersen <12519942+ryanchristo@users.noreply.github.com>

* chore: expand test fields

* refactor: use SdkIntTrim

* chore: spacing

* chore: comment out buyorder reliant code

Co-authored-by: technicallyty <48813565+tytech3@users.noreply.github.com>
Co-authored-by: Ryan Christoffersen <12519942+ryanchristo@users.noreply.github.com>