Use hardcoded Tap Domain Separator from tap-core

[gusinacio]

tap-core has a tap_eip712_domain function that uses the hardcoded name and version. We had some problems in the past with mismatch between those, let's just use this function.

https://docs.rs/tap_core/latest/tap_core/fn.tap_eip712_domain.html

[gusinacio]

We could move the DOMAIN_SEPARATOR to tap-core to prevent mismatches on any side.

[YashBit]

@gusinacio Please can you assign this to me?

[gusinacio]

@YashBit just assigned to you. Also added some description.