allow omitting package scope in --filter (like pnpm does)

[stefanprobst]

Goals

align behavior of --filter with pnpm, which allows to omit the scope/namespace from workspace package names.

# does not work
turbo -F db build
# only this works
turbo -F @repo/db build

# works
pnpm -F db build

Background

see https://pnpm.io/filtering#--filter-package_name

"Specifying the scope of the package is optional"

Proposal

no

[anthonyshew]

This used to be the behavior the there were sublte bugs and inconsistencies that would occur because of this behavior. We won't be reverting on this one.