SkPDF: in-place font subsetting

Motivation: gross code simplification, also no bitset lookups at draw time.

SkPDFFont owns its glyph useage bitset.

SkPDFSubstituteMap goes away.

SkPDFObject interface is simplified.

SkPDFDocument tracks font usage (as hash set), not glyph usage.

SkPDFFont gets a simpler constructor.

SkPDFFont has first and last glyph set in constructor, not adjusted later.

SkPDFFont implementations are simplified.

SkPDFGlyphSet is replaced with simple SkBitSet.

SkPDFFont sizes its SkBitSets based on glyph count.

SkPDFGlyphSetMap goes away.

SkBitSet is now non-copyable.

SkBitSet now how utility methods to match old SkPDFGlyphSet.

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2253283004

CQ_INCLUDE_TRYBOTS=master.client.skia:Test-Win-MSVC-GCE-CPU-AVX2-x86_64-Release-GDI-Trybot,Test-Win-MSVC-GCE-CPU-AVX2-x86_64-Debug-GDI-Trybot

Review-Url: https://codereview.chromium.org/2253283004
diff --git a/src/pdf/SkPDFMetadata.cpp b/src/pdf/SkPDFMetadata.cpp
index 2592496..46fe461 100644
--- a/src/pdf/SkPDFMetadata.cpp
+++ b/src/pdf/SkPDFMetadata.cpp
@@ -168,12 +168,11 @@
 public:
     PDFXMLObject(SkString xml) : fXML(std::move(xml)) {}
     void emitObject(SkWStream* stream,
-                    const SkPDFObjNumMap& omap,
-                    const SkPDFSubstituteMap& smap) const override {
+                    const SkPDFObjNumMap& omap) const override {
         SkPDFDict dict("Metadata");
         dict.insertName("Subtype", "XML");
         dict.insertInt("Length", fXML.size());
-        dict.emitObject(stream, omap, smap);
+        dict.emitObject(stream, omap);
         static const char streamBegin[] = " stream\n";
         stream->write(streamBegin, strlen(streamBegin));
         // Do not compress this.  The standard requires that a