Make CELFormatterCommandParser function without a thread-singleton

[ravenblackx]

Commit Message: Make CELFormatterCommandParser function without a thread-singleton
Additional Description: Previously, initializing a CELFormatterCommandParser (e.g. from yaml instantiating a SubstitutionFormatString) uses the ServerConfigurationFactoryContext singleton, which only works after server initialization. This means that in tests an ASSERT fails: ThreadLocalInjectableSingleton used prior to initialization. In unit tests this can be mitigated by initializing a ScopedThreadLocalServerContextSetter, but this issue also occurs in the config validator used by CI. Rather than making that test also work around this issue, we can use the GenericFactoryContext that's available in this code path to initialize a reference with the required context via proper dependency injection.

There's a second initialization path that doesn't have a FactoryContext available, so that one still uses the singleton, to initialize the injected reference - the path that checks configs doesn't use that path, so this solves the immediate problem.
Risk Level: Negative, it fixes an issue and changes no behavior except making for fewer touches of a singleton-instance.
Testing: Updated tests to use the modified constructor.
Docs Changes: n/a
Release Notes: n/a
Platform Specific Features: n/a

[ravenblackx]

Ugh, never mind, the BuiltInCommandParserFactory initialization occurs before the singleton is initialized, making it a much bigger deal to refactor.