Change profile inline cache threshold to 4000.

The value 4000 is decided based on a local experiment. It increases the
number of inline caches while resulting in 10% or less incomplete inline
caches on typical apps. More details are in b/309434431.

Bug: 309434431
Change-Id: Id8a4f1fcad21aa38ceef972d5ef85eb098f4bb8f
Test: Presubmit