RFR: 8303900: Rename BitMap search functions

[Kim Barrett]

Please review this renaming of the following functions in BitMap:

get_next_one_offset => find_first_set_bit
get_next_zero_offset => find_first_clear_bit
get_next_one_offset_aligned_right => find_first_set_bit_aligned_right

Note that ShenandoahMarkBitMap::get_next_one_offset is not being renamed.  For
some reason that class contains a copy of a sizable chunk of the code from
some version of BitMap.  (Not sure why it doesn't use an internal BitMapView
rather than code copying.)

Testing:
mach5 tier1-5

-------------

Commit messages:
 - update gtests
 - update shenandoah uses
 - update zgc uses
 - update gc/shared uses
 - update Parallel uses
 - update G1 uses
 - rename functions

Changes: https://git.openjdk.org/jdk/pull/12951/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12951&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303900
  Stats: 75 lines in 12 files changed: 0 ins; 0 del; 75 mod
  Patch: https://git.openjdk.org/jdk/pull/12951.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12951/head:pull/12951

PR: https://git.openjdk.org/jdk/pull/12951