adb: fix escape_arg for multiple quotes

escape_arg reuses the same index for the source (s) and the destination
(result), so it breaks on strings containing more than one quote, e.g:

 * a'b'c    ==> 'a'\''b'c'
 * a'bcde'f ==> 'a'\''b'\'cde'f'

Also make the function more efficient by doing fewer string copies. This
code is based on the android::base::Split code.

Use EXPECT_EQ because the tests can keep going if one fails.

Bug: none
Test: adb_test --gtest_filter=adb_utils.escape_arg
Change-Id: I6ca6e905fa53cc61b9a87276cb7116a5df7e8017