Fix double bolding

resolveStyle increases minikinStyle's weight value based on Skia's style
value. Since we compute Skia's style based on given weight value, we
should not add extra bold weight to minikinStyle.

This CL also fixes misunderstanding of base weight.
The base weight is only used for computing weight relative to the
weighted alias. Thus, base weight should not be updated except for
createWeightAlias method.

To be clear, this CL changes the function names but keeps the same
semantics as before.

Test: adb shell /data/nativetest/hwui_unit_tests/hwui_unit_tests
Test: am instrument -w -e class android.graphics.cts.TypefaceTest\
      android.graphics.cts/android.support.test.runner.AndroidJUnitRunner
Bug: 37880319

Change-Id: Ied73189b11792fb062da46f45afd2db664e6ecb4