[Exclusivity] Change the exclusivity checks inline heuristic threshold

[shajrawi]

radar rdar://problem/46783598

This PR reduces the aggressiveness of the exclusivity checks inline heuristic: based on local testing, I believe I found a sweet-spot between maintaining -O performance and making sure we do not increase the code size (too much) - will use this PR to test on the bots before committing.

[shajrawi]

@swift-ci Please smoke test

[shajrawi]

@swift-ci Please benchmark

[swift-ci]

Build comment file:

Performance: -O

TEST	OLD	NEW	DELTA	RATIO
Improvement
Dictionary4OfObjects	316	268	-15.2%	1.18x

Code size: -O

TEST	OLD	NEW	DELTA	RATIO
Regression
DictTest4Legacy.o	25540	27569	+7.9%	0.93x
DictTest4.o	24034	25887	+7.7%	0.93x
Improvement
Hash.o	34025	28585	-16.0%	1.19x
DictionaryRemove.o	17125	15461	-9.7%	1.11x
DictionarySwap.o	26414	24798	-6.1%	1.07x
DictTest2.o	15547	14747	-5.1%	1.05x
RGBHistogram.o	27331	26054	-4.7%	1.05x
SetTests.o	74711	71591	-4.2%	1.04x
DictTest.o	19254	18454	-4.2%	1.04x
DictTest3.o	22507	21707	-3.6%	1.04x
DriverUtils.o	144693	142621	-1.4%	1.01x

Performance: -Osize

TEST	OLD	NEW	DELTA	RATIO
Regression
ObjectiveCBridgeFromNSArrayAnyObjectForced	3919	4364	+11.4%	0.90x

Code size: -Osize

TEST	OLD	NEW	DELTA	RATIO
Regression
DictionarySwap.o	22166	26422	+19.2%	0.84x
RGBHistogram.o	23974	24582	+2.5%	0.98x
DictionaryGroup.o	14159	14367	+1.5%	0.99x
Improvement
DictTest4.o	16894	14958	-11.5%	1.13x
SetTests.o	66743	61335	-8.1%	1.09x
DictionarySubscriptDefault.o	19777	18753	-5.2%	1.05x

How to read the data

The tables contain differences in performance which are larger than 8% and differences in code size which are larger than 1%.

If you see any unexpected regressions, you should consider fixing the
regressions before you merge the PR.

Noise: Sometimes the performance results (not code size!) contain false
alarms. Unexpected regressions which are marked with '(?)' are probably noise.
If you see regressions which you cannot explain you can try to run the
benchmarks again. If regressions still show up, please consult with the
performance team (@eeckstein).

Hardware Overview

  Model Name: Mac Pro
  Model Identifier: MacPro6,1
  Processor Name: 8-Core Intel Xeon E5
  Processor Speed: 3 GHz
  Number of Processors: 1
  Total Number of Cores: 8
  L2 Cache (per Core): 256 KB
  L3 Cache: 25 MB
  Memory: 64 GB

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