Bold StyleSpan further for auto-bold

StyleSpan with Typeface.BOLD will only bold if the text doesn't already
have a BOLD style. But auto-bolded text needs to be further bolded.
If the Typeface style is BOLD, bold more for auto-bold.
(The fake bold works for Typefaces with weight < 700)

NOTE: This backports a public API change from master
 but hides the public methods, so that we can use the new
 feature in SystemUI, which has access to hidden APIs.
This does NOT backport the changes to HTML or StringBlock
 as those changes may have broad affects that we do not
 have time to validate before release.

Test: manual - settings page, example StyleSpans,
atest StyleSpanTest TextViewTests
Bug: 175177807
Bug: 208592419

Merged-In: Iec7db7eadd18ed6a2efc6ee39b49c1d6cb15d870
Change-Id: I8da1d3f903b265e0331e7166a0afa0720c0eaa01