Enable linter: prealloc

[rootulp]

Context

https://github.com/celestiaorg/celestia-app/pull/666#discussion_r959704855

Description

We want to enable the prealloc linter to reduce PR feedback cycles and increase codebase consistency.

• [ ] Confirm that prealloc throws a warning / error when slices are declared without pre-allocating their length
• [ ] Once confirmed, enable the linter in .golangci.yml

Links

• https://golangci-lint.run/usage/linters/#prealloc