buildozer: do not remove visibility from macros or loaded rules in fix

Previously, buildozer's removeVisibility routine stripped visibility
attributes (such as "//visibility:private" or matching package default_visibility)
from any rule whose visibility matched defaultVisibility.

However, Starlark macros and loaded rules frequently implement custom fallback
visibility logic (e.g. falling back to a non-private default if visibility
is omitted). Stripping visibility from such macros causes them to silently
broaden their visibility.

Skip visibility removal if a rule's kind contains a dot (indicating a dotted
macro or module) or matches any symbol loaded via a load() statement in the
BUILD file.