Include blockheight filter in `getfixedintervalprice` and `listfixedintervalprice`

#### What would you like to be added:
Add a optional parameter `height` to `getfixedintervalprice` & `listfixedintervalprice` be able to filter price in a specific blockheight:

`getfixedintervalprice { "fixedIntervalPriceId" : "DFI/USDC", "height" : "1234" }`
`listfixedintervalprice { "height" : "1234" }`

#### Why is this needed:
This will help external applications to build historical data & check price at specific time/blockheight.

#### Note
This change requires modification in how fixedintervalprice is stored in DB so introducing this feature will lead to a full reindex required