Remove one layer of abstraction and multiple intermediate types

[adamsitnik]

It's #2033 + one commit: 1aa6937 I did not want to include it in #2023 as it would make reviewing hard. I am going to make it a draft for now and make it ready for review when #2033 is merged.

Explanation: In #2033 I've moved most of the validation logic to the CommandResult, making ParseResultVisitor a very simple class. This included moving all hacks from ParseResultVisitor to earlier stages of parsing. Thanks to that, we can make ParseOperation create SymbolResult instances directly, rather than creating intermediate SyntaxNode instaces and later letting ParseResultVisitor to map it to SymbolResult instances.

This has a really nice impact on startup performance. The number of JIT compiled methods drops from 221 to 198, the startup improves by 1-2ms for the simple case scenario.

Method	Args	Mean	Ratio
Empty		67.62 ms	0.81
EmptyAOT		13.27 ms	0.16
Corefxlab		83.71 ms	1.00
SystemCommandLine2021		101.97 ms	1.22
SystemCommandLine2022		84.46 ms	1.01
SystemCommandLineNow		83.60 ms	1.00
SystemCommandLineNowR2R		77.46 ms	0.93
SystemCommandLineNowAOT		12.81 ms	0.15
Empty	--bool -s test	64.42 ms	0.73
EmptyAOT	--bool -s test	12.57 ms	0.14
Corefxlab	--bool -s test	84.14 ms	0.95
SystemCommandLine2021	--bool -s test	105.74 ms	1.19
SystemCommandLine2022	--bool -s test	90.46 ms	1.02
SystemCommandLineNow	--bool -s test	88.85 ms	1.00
SystemCommandLineNowR2R	--bool -s test	80.65 ms	0.91
SystemCommandLineNowAOT	--bool -s test	12.99 ms	0.15

The allocaitons drop is also very nice: few hundreds of bytes for simple scenario.

[adamsitnik]

Closing in favor of #2040