Printer: synthetic members are not filtered from output

[rochala]

Compiler-generated members show up in get/get-external output, drowning out the real API.

Repro:

cellar get-external com.lihaoyi:os-lib_3:latest os.proc
cellar get-external com.lihaoyi:requests_3:latest requests.Requester

Observed (mixed into real members):

def call$default$2Map[Predef.String, Predef.String]   // default-getter methods
def stream$default$22Function1[StreamHeaders, Unit]
symbol[Mirror.MirroredElemLabels]                      // Mirror synthetics on case-class companions
symbol[Mirror.MirroredLabel]
def <clinit>(): Unit                                   // static initializer (StringUtils)
def <init>(): Unit                                     // repeated several times in one listing

For requests.Requester the synthetic $default$N getters outnumber the real methods, so with --limit 8 the listing shows almost nothing but synthetics.

Expected: default-parameter getters, Mirror synthetics, <clinit>, and duplicate constructors are filtered (or at least hidden by default behind a flag). Default arguments would ideally surface as = <default> markers on the corresponding parameters instead.