Optimize low hanging fruit

[JimBobSquarePants]

Prerequisites

• I have written a descriptive pull-request title
• I have verified that there are no overlapping pull-requests open
• I have verified that I am following matches the existing coding patterns and practice as demonstrated in the repository. These follow strict Stylecop rules 👮.
• I have provided test coverage for my change (where applicable)

Description

I did a little tracing to see if there were any obvious bottlenecks. We get a nice speedup over longer text. I also made our lazy instances thread safe.

Also includes a fix for #383

BenchmarkDotNet=v0.13.1, OS=Windows 10.0.22631
11th Gen Intel Core i7-11370H 3.30GHz, 1 CPU, 8 logical and 4 physical cores
.NET SDK=8.0.200-preview.23624.5
  [Host]   : .NET 6.0.26 (6.0.2623.60508), X64 RyuJIT
  ShortRun : .NET 6.0.26 (6.0.2623.60508), X64 RyuJIT

Job=ShortRun  IterationCount=3  LaunchCount=1
WarmupCount=3

PR

Method	Text	Mean	Error	StdDev
SixLaborsFonts	Lore(...)tus. [2477]	19,515.541 us	3,656.2844 us	200.4133 us

Main

Method	Text	Mean	Error	StdDev
SixLaborsFonts	Lore(...)tus. [2477]	20,980.555 us	8,470.2382 us	464.2823 us