Avoid state machines

[lahma]

Targeted the most obvious choices (often used or simple to change). If was the beast here and I'm sure the coded didn't get too clear by the change. Maybe judge that by the results - it's ugly but so often invoked...

BenchmarkDotNet=v0.12.1, OS=Windows 10.0.19042
Intel Core i7-6820HQ CPU 2.70GHz (Skylake), 1 CPU, 8 logical and 4 physical cores
.NET Core SDK=5.0.202
  [Host]     : .NET Core 5.0.5 (CoreCLR 5.0.521.16609, CoreFX 5.0.521.16609), X64 RyuJIT
  DefaultJob : .NET Core 5.0.5 (CoreCLR 5.0.521.16609, CoreFX 5.0.521.16609), X64 RyuJIT

Fluid.Benchmarks.TagBenchmarks

Diff	Method	Mean	Error	Gen 0	Gen 1	Gen 2	Allocated
Old	RawTag_Parse	1,403.9 ns	12.71 ns	0.1125	0.0000	0.0000	472 B
New		1,363.40 ns (-3%)	8.817 ns	0.1125 (0%)	0.0000	0.0000	472 B (0%)
Old	RawTag_Render	202.1 ns	0.25 ns	0.0458	0.0000	0.0000	192 B
New		142.58 ns (-29%)	0.419 ns	0.0458 (0%)	0.0000	0.0000	192 B (0%)
Old	IfStatement_Ands_Parse	2,933.6 ns	14.34 ns	0.2556	0.0000	0.0000	1080 B
New		2,937.76 ns (0%)	10.568 ns	0.2556 (0%)	0.0000	0.0000	1080 B (0%)
Old	IfStatement_Ands_Render	276.9 ns	0.37 ns	0.0134	0.0000	0.0000	56 B
New		159.17 ns (-43%)	0.387 ns	0.0134 (0%)	0.0000	0.0000	56 B (0%)
Old	IfStatement_Ors_Parse	2,778.1 ns	18.82 ns	0.2480	0.0000	0.0000	1048 B
New		2,831.34 ns (+2%)	12.927 ns	0.2480 (0%)	0.0000	0.0000	1048 B (0%)
Old	IfStatement_Ors_Render	284.9 ns	0.79 ns	0.0134	0.0000	0.0000	56 B
New		163.08 ns (-43%)	0.494 ns	0.0134 (0%)	0.0000	0.0000	56 B (0%)
Old	ElseIfStatement_Parse	3,656.2 ns	34.29 ns	0.3128	0.0000	0.0000	1320 B
New		3,719.81 ns (+2%)	20.734 ns	0.3128 (0%)	0.0000	0.0000	1320 B (0%)
Old	ElseIfStatement_Render	320.0 ns	1.36 ns	0.0134	0.0000	0.0000	56 B
New		165.62 ns (-48%)	0.825 ns	0.0134 (0%)	0.0000	0.0000	56 B (0%)
Old	Assign_Parse	3,322.4 ns	11.51 ns	0.3204	0.0000	0.0000	1352 B
New		3,292.75 ns (-1%)	12.106 ns	0.3204 (0%)	0.0000	0.0000	1352 B (0%)
Old	Assign_Render	367.3 ns	0.78 ns	0.0205	0.0000	0.0000	88 B
New		271.46 ns (-26%)	2.938 ns	0.0210 (+2%)	0.0000	0.0000	88 B (0%)
Old	Else_Parse	2,098.0 ns	17.45 ns	0.1945	0.0000	0.0000	816 B
New		2,131.72 ns (+2%)	19.065 ns	0.1945 (0%)	0.0000	0.0000	816 B (0%)
Old	Else_Render	185.0 ns	0.18 ns	0.0210	0.0000	0.0000	88 B
New		105.97 ns (-43%)	0.224 ns	0.0210 (0%)	0.0000	0.0000	88 B (0%)
Old	TextSpan_Parse	307.8 ns	0.97 ns	0.0782	0.0000	0.0000	328 B
New		326.10 ns (+6%)	3.839 ns	0.0782 (0%)	0.0000	0.0000	328 B (0%)
Old	TextSpan_Render	103.2 ns	0.34 ns	0.0210	0.0000	0.0000	88 B
New		85.66 ns (-17%)	0.420 ns	0.0210 (0%)	0.0000	0.0000	88 B (0%)

Fluid.Benchmarks.FluidBenchmarks

Diff	Method	Mean	Error	Gen 0	Gen 1	Gen 2	Allocated
Old	Parse	8.874 μs	0.1658 μs	0.6561	0.0000	0.0000	2.71 KB
New		8.627 μs (-3%)	0.1179 μs	0.6561 (0%)	0.0000	0.0000	2.71 KB (0%)
Old	ParseBig	49.396 μs	0.9814 μs	2.9297	0.0610	0.0000	12.13 KB
New		50.067 μs (+1%)	0.3050 μs	2.9297 (0%)	0.0000 (-100%)	0.0000	12.13 KB (0%)
Old	Render	638.494 μs	2.5238 μs	22.4609	4.8828	0.0000	95.75 KB
New		599.048 μs (-6%)	2.1111 μs	22.4609 (0%)	4.8828 (0%)	0.0000	95.75 KB (0%)
Old	ParseAndRender	643.862 μs	2.1457 μs	23.4375	4.8828	0.0000	98.93 KB
New		611.502 μs (-5%)	3.2349 μs	23.4375 (0%)	4.8828 (0%)	0.0000	98.93 KB (0%)