chore(tests): Use `go:embed` for long result hex in runtime/exports_test.go

Certain tests use long result hex to test encoding/decoding of types. They are currently stored in a variable with linter disabled. These can get very long and we need to tidy it up.

I am unaware of all the tests. Here's one I could find: https://github.com/ChainSafe/gossamer/blob/development/dot/import_integration_test.go#L69

Searching for `//nolint:lll` could help find them.

_Originally posted by @timwu20 in https://github.com/ChainSafe/gossamer/pull/3297#discussion_r1224381231_