add foundation treasury feature to x/foundation

[0Tech]

Summary

add foundation treasury feature to x/foundation.

Proposal

1. The chain collects another tax which is the main source of the foundation treasury.
   • x/foundation sends certain amount of coins from the "fee-collector" to its module account "treasury" BEFORE the x/distribution touches it.
   • The default percentage would be 0%. You may change the percentage in the genesis.
2. Only the authorized operator can withdraw coins from the module account.

TODO: add items after the confirmation.

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