add Statemint <--> Acala

[StrawberryFlavor]

Statemint <--> Acala USDT
decimals: 6
acala 上 ForeignAssetId 为 12，minimalBalance 10,000
statemint 上 id 1984, minBalance: 700,000

statemint --> acala
enconded call data: 0x1f0801010100411f0100010100c0997c4f2b3a83eb07ef74a867cf672a25a2a30cc61abc936dcc994df77ba84a0104000002043205011f0002093d000000000000
Destination Chain Transfer Fee 为 808
需要注意的是，无法全部转走，statemint上需要保留 e.d, 即 minBalance: 700,000

acala --> statemint
enconded call data:
0x36010100010300a10f043205011f0002093d0001010200a10f0100c0997c4f2b3a83eb07ef74a867cf672a25a2a30cc61abc936dcc994df77ba84a00
Destination Chain Transfer Fee 为 700,000
需要注意的是，由于 Destination Chain Transfer Fee 跟 e.d 都为 700,000，因此在 acala 直接将 usdt 跨链到 statemint 上没有 usdt 的账户时，转账数量需要大于 1,400,000