Fix assumption that macOS filesystem is case sensitive

[karrtikr]

The default filesystem on Darwin is case insensitive: #22006. Look for all instances of places where we are only assuming Windows is case insensitive (converting paths to upper case or lower case just for windows). For eg.

• vscode-python/src/client/pythonEnvironments/common/externalDependencies.ts

  Lines 88 to 90 in be334bd

  	export function normCasePath(filePath: string): string {
  	return getOSType() === OSType.Windows ? path.normalize(filePath).toUpperCase() : path.normalize(filePath);
  	}

• vscode-python/src/client/common/platform/fs-paths.ts

  Lines 151 to 153 in d613776

  	export function normCase(s: string): string {
  	return getOSType() === OSType.Windows ? s.toUpperCase() : s;
  	}

• ...maybe more

And change it to also include macOS in that list. Note this may alter IDs for environments in macOS:

vscode-python/src/client/pythonEnvironments/base/info/env.ts

Lines 245 to 250 in 15bb974

	/**
	* Gets general unique identifier for most environments.
	*/
	export function getEnvID(interpreterPath: string, envFolderPath?: string): string {
	return normCasePath(getEnvPath(interpreterPath, envFolderPath).path);
	}

So we should probably clear any existing environments discovered for macOS, simple way to do that is use a new key here, like PYTHON_ENV_INFO_CACHEv2:

vscode-python/src/client/pythonEnvironments/index.ts

Line 70 in 2442dfb

const wasTriggered = getGlobalStorage<PythonEnvInfo[]>(ext.context, 'PYTHON_ENV_INFO_CACHE', []).get().length > 0;