Copy asan_rtl.* and agent_logger.exe to the syzygy directory for the ASan builds.

This is my second attempt to do this, the first time https://codereview.chromium.org/23460023/ has been reverted (https://codereview.chromium.org/23858006) because the new target 'copy_syzyasan_binaries' was not build, so the SyzyASan binaries were missing from the syzygy dir...

Currently the syzygy_optimize script was taking care of copying asan_rtl.[dll|pdb] to the syzygy directory, this was causing 2 warnings when building a SyzyASan splitted build with ninja:

- ninja: warning: multiple rules generate syzygy\asan_rtl.dll. builds involving this target will not be correct; continuing anyway
- ninja: warning: multiple rules generate syzygy\asan_rtl.dll.pdb. builds involving this target will not be correct; continuing anyway

The multiple rules come from the fact that both syzygy\chrome.dll and syzygy\chrome_child.dll were trying to generate those artifacts.

I've also added agent_logger.exe to the syzygy directory, with this it'll be easier for the person grabing a SyzyASan build from the LKGR builder to use it.

I've also removed all the "--agent-dll" logic from syzygy_instrument.py as it was only copying the asan binaries to the syzygy directory, it's now done directly in the 'copy_syzyasan_binaries' gyp target.

R=chrisha@chromium.org
BUG=

Review URL: https://codereview.chromium.org/25890006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229085 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229085