Rename enableGwpAsan manifest attribute.

It's now gwpAsanMode=never|always instead of a boolean.

Bug: 151262688
Test: CtsGwpAsanTestCases
Exempt-From-Owner-Approval: cherrypick
Merged-Id: I6104524853cf76457ba9c40375a2cc12dbdc128b
Change-Id: I6104524853cf76457ba9c40375a2cc12dbdc128b
(cherry picked from commit 0e2da287341be510cfac923f2b53b61a570edade)