ci(deps): enable testifylint linter on .*_test.go$

[mmorel-35]

Description

enable testifylint linter on .*_test.go$

It helps applying the best practices with testify use

It applies empty, error-nil and error-is-as rules. Several are excluded to avoid having a too big PR.

The .*_test.go$ has been removed from exclude-files and moved to exclude-rules

[simar7]

I briefly went over the changes and it seems reasonable to me. But I'll wait for others to reply.

I haven't used this linter in the past and the runtime is of concern to me.

[knqyf263]

Linters can sometimes be too noisy, so let's introduce it once and see how it goes for a while.