Pass -fvisibility=hidden to profiler modules. (#16335)

Pass -fvisibility=hidden to profiler modules. (#16335)

* Pass -fvisibility=hidden to profiler modules.

This appears to not break the profilers:

```
directhex@breakfast:/tmp$ nm -g /tmp/ponyponyponypony/lib/libmono-profiler-log.so | grep close_socket_fd
directhex@breakfast:/tmp$
directhex@breakfast:/tmp$ /tmp/ponyponyponypony/bin/mono --profile=log:report bottle.exe
99 bottles of beer on the wall, 99 bottles of beer.
Take one down and pass it around, 99 bottles of beer on the wall.

[..]

No more bottles of beer on the wall, no more bottles of beer.
Go to the store and buy some more, 99 bottles of beer on the wall.

Mono log profiler data
	Profiler version: 3.0
	Data version: 17
	Arguments: log:report
	Architecture: x86-64
	Operating system: linux
	Mean timer overhead: 86 nanoseconds
	Program startup: Mon Aug 19 14:18:30 2019
	Program ID: 17715
	Server listening on: 41539

JIT summary
	Compiled methods: 753
	Generated code size: 228046
	JIT helpers: 0
	JIT helpers code size: 0

GC summary
	GC resizes: 0
	Max heap size: 0
	Object moves: 0

Metadata summary
	Loaded images: 3
	Loaded assemblies: 3

Exception summary
	Throws: 0
	Executed finally clauses: 3

Thread summary
	Thread: 0x7fcd968c9700, name: "Finalizer"
	Thread: 0x7fcd966c8700, name: "Profiler Sampler"
	Thread: 0x7fcd9b036780, name: "Main"
	Thread: 0x7fcd964c7700, name: "Profiler Helper"
	Thread: 0x7fcd954c5700, name: "Profiler Dumper"
	Thread: 0x7fcd95cc6700, name: "Profiler Writer"

Domain summary
	Domain: (nil), friendly name: "bottle.exe"

Context summary
	Context: (nil), domain: (nil)

Counters:
	Mono System:
		User Time                      : 70.000ms
		System Time                    : 0.000ms
		Total Time                     : 140.000ms
		Working Set                    : 22032384
		Private Bytes                  : 63455232
		Virtual Bytes                  : 449630208
		Page Faults                    : 3004
		CPU Load Average - 1min        : 1.870000
		CPU Load Average - 5min        : 2.670000
		CPU Load Average - 15min       : 2.900000
	Mono JIT:
		Methods from AOT               : 536
		Methods JITted using mono JIT  : 154
		Methods JITted using LLVM      : 0

```

* Add missing annotations and includes