Fix EscapeAnalysis value_to_bridge_object and strong_copy_unowned_value.

[atrick]

Noticed via code inspection. This could potentially miscompile, but we
haven't seen that happen to my knowledge.

Both value_to_bridge_object and strong_copy_XXX need to escape their
resulting value.

The implementation seemed to assume that it is conservatively correct
simply to avoid building a connection graph node for an value. This is
not true. Any value that has a pointer type requires a connection
graph node. The only way to be conservative is to create the value
node and point it to an escaping content node.

We can always declare that certain special types are not considered
pointer types, but then we need to handle all conversions from those
types to pointer types by escaping the resulting
pointer. BridgeObjects are often on the performance-critical path.

[atrick]

@swift-ci test

[atrick]

@swift-ci test source compatibility

[atrick]

@swift-ci benchmark

[swift-ci]

Performance: -O

Code size: -O

Performance: -Osize

Code size: -Osize

Performance: -Onone

Regression	OLD	NEW	DELTA	RATIO
ObjectiveCBridgeFromNSArrayAnyObjectForced	6940	7900	+13.8%	0.88x (?)
Improvement	OLD	NEW	DELTA	RATIO
NSStringConversion.MutableCopy.Rebridge.UTF8	734	677	-7.8%	1.08x (?)

Code size: -swiftlibs

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