Add support for INTR and IBTC prices

[ebma]

Context

Pendulum might need to have access to the IBTC and INTR prices on chain. These are currently not supported by the batching server.

TODO

Append the mapping here with:

...
("INTERLAY", "INTR") => Some("interlay".to_string()),
("INTERBTC", "IBTC") => Some("interbtc".to_string()),
...

and add respective test cases.

[ebma]

@pendulum-chain/product this is a follow-up for https://github.com/pendulum-chain/transaction-builder/pull/127. It might not be very relevant if we don't need prices for INTR or IBTC on chain but since this is a simple addition, we can just add the support already.

[prayagd]

Hey team! Please add your planning poker estimate with Zenhub @b-yap @ebma @gianfra-t @TorstenStueber

[TorstenStueber]

@pendulum-chain/product can we move to Ready or not relevant anymore?

[prayagd]

Dont have the full context cc @vadaynujra