Add support for DOTNET prefix on ICorProfiler env vars (#117902)

[barosiak]

Add DOTNET_* variations to existing CORECLR_* profiler environment variables.

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[barosiak]

@dotnet-policy-service agree company="Microsoft"

[noahfalk]

Congrats on the first PR! Everything here looks like it works so adding a few suggestions to refine it :)

[noahfalk]

Suggested change

	The profiler environment variables now support both `DOTNET` and `CORECLR` prefixes. The `DOTNET` prefix is the new standard, while `CORECLR` is maintained for backwards compatibility and may be removed in the future. **Do not mix both conventions in a project** as this will result in errors. New projects should use the `DOTNET` prefix.
	Starting in .NET 11, profiler environment variables now support both `DOTNET` and `CORECLR` prefixes. The `DOTNET` prefix is the new standard, while `CORECLR` is maintained for backwards compatibility and may be removed in the future. **Do not mix both conventions in a project** as this will result in errors. New projects should use the `DOTNET` prefix.

[noahfalk]

This looks like it would work but instead of defining all these variables twice perhaps we could tweak the existing fallback behavior a little bit in order to use it? Something like:

RETAIL_CONFIG_DWORD_INFO_EX(EXTERNAL_CORECLR_ENABLE_PROFILING, W("ENABLE_PROFILING"), 0, "CoreCLR
only: Flag to indicate whether profiling should be enabled for the currently running 
process.", CLRConfig::LookupOptions::CoreclrFallbackPrefix)

Then over in clrconfig.cpp

bool coreclrPrefix = CheckLookupOption(options, LookupOptions::CoreclrFallbackPrefix);
fallbackPrefix = coreclrPrefix ? CORECLR_PREFIX : COMPLUS_PREFIX;

And in the cache

if(matchC)
{
    if(SString::_wcsnicmp(wszName, COMPLUS_PREFIX, LEN_OF_COMPLUS_PREFIX) == 0)
    {
        wszName += LEN_OF_COMPLUS_PREFIX;
        s_EnvNames.Add(wszName, (DWORD) (wszCurr - wszName));
    }
    else if(SString::_wcsnicmp(wszName, CORECLR_PREFIX, LEN_OF_CORECLR_PREFIX) == 0)
    {
        wszName += LEN_OF_CORECLR_PREFIX;
        s_EnvNames.Add(wszName, (DWORD) (wszCurr - wszName));
    }
}

[noahfalk]

Rather than running every profiler test twice with old and new variables we can probably get nearly the same test coverage and speed things up by picking one regular profiler test and one notification profiler test to run duplicated. Individually the tests probably run pretty fast but its easy for the cost to creep up when we create these multipliers.

[jkotas]

This should be also documented in https://learn.microsoft.com/en-us/dotnet/core/runtime-config/debugging-profiling . The source for the official documentation lives at https://github.com/dotnet/docs/blob/main/docs/core/runtime-config/debugging-profiling.md

It may be best to delete the redundant documentation here and merge this doc into the official docs.

[jkotas]

These config settings are missing in the docs

[am11]

1. For other configs, the precedence order is DOTNET_ then whatever the legacy prefix was.
2. GetConfigValue supports both prefixes. The way it works is; we define the unprefixed knob in configvalues, and let GetConfigValue handle the prefixes and their precedence.