consider alternative approach to loading MASP params

[tzemanovic]

In #4251 we had to workaround API requiring MASP params even in cases where those might not be needed (in there it's a workaround for IBC transfer that's not shielded). The solution was to try to continue constructing the tx even if loading params fails.

from @murisi's description

An alternative approach to this PR could be to determine the precise conditions under which MASP build parameters would be required, and only do generation in those circumstances. This also would work fine, but would involve making sure that the determined conditions do not fall out of sync with the transaction building code that follows its usage.