Increase threshold for profile compilation

Threshold to trigger compilation based on profiles has been increase
to avoid re-compilation too frequenctly.
Now compilation will take place if methods/classes in the new profile exceeds
by maximum of the following:
- 2% methods/classes in the existing profile.
- 100 methods or 50 classes.

Context for above numbers:
I analyzed profiles on my local device. Average number of methods and classes
in the profiles were 8000 and 2500 respectively.

Also added tests for the same.

Bug: 66732454
Test: test-art-host-gtest-profile_assistant_test
Change-Id: I8a9034c543a53a1c7b2a18a91d560786391b7c6e