Refactor secret management providers and introduce unified handling

- Removed KeePass and SecretStore provider implementations.
- Integrated KeePass and SecretStore as vaults under the SecretManagement provider.
- Added new functions: Get-DSCConfigurationDataCredentialProvider and Set-DSCConfigurationDataCredentialProvider for managing credential providers.
- Implemented Unlock-ConfigurationDataSecretManagementVault to handle vault unlocking with master passwords.
- Updated README to reflect changes in provider usage and examples.
- Enhanced error handling and validation for vault registration and settings.

Private/Unlock-ConfigurationDataSecretManagementVault.ps1

@@ -0,0 +1,49 @@
+function Unlock-ConfigurationDataSecretManagementVault {
+    [CmdletBinding()]
+    Param(
+        [Parameter(Mandatory=$false)]
+        [hashtable]
+        $ProviderSettings = @{}
+    )
+
+    if(-not $ProviderSettings.ContainsKey("SecretManagement")){
+        return
+    }
+
+    $SecretManagementSettings = $ProviderSettings.SecretManagement
+    if(-not ($SecretManagementSettings -is [System.Collections.IDictionary])){
+        return
+    }
+
+    if(-not (Test-ConfigurationDataMapContainsKey -Map $SecretManagementSettings -Key "MasterPassword")){
+        return
+    }
+
+    $Vault = [string](Get-ConfigurationDataMapValue -Map $SecretManagementSettings -Key "DefaultVault" -DefaultValue "")
+    if([string]::IsNullOrWhiteSpace($Vault)){
+        throw "SecretManagement provider settings define [MasterPassword], but [DefaultVault] is not defined."
+    }
+
+    $UnlockSecretVaultCommand = Get-Command -Name Unlock-SecretVault -ErrorAction SilentlyContinue
+    if($null -eq $UnlockSecretVaultCommand){
+        throw "Command [Unlock-SecretVault] was not found. Install module [Microsoft.PowerShell.SecretManagement]."
+    }
+
+    $MasterPassword = Resolve-ConfigurationDataProviderSecureString -Value $SecretManagementSettings.MasterPassword
+    & $UnlockSecretVaultCommand -Name $Vault -Password $MasterPassword
+
+    $TestSecretVaultCommand = Get-Command -Name Test-SecretVault -ErrorAction SilentlyContinue
+    if($null -ne $TestSecretVaultCommand){
+        $IsUnlocked = $false
+        try {
+            $IsUnlocked = [bool](& $TestSecretVaultCommand -Name $Vault -ErrorAction Stop)
+        }
+        catch {
+            throw "SecretManagement vault [$Vault] could not be unlocked. $($_.Exception.Message)"
+        }
+
+        if(-not $IsUnlocked){
+            throw "SecretManagement vault [$Vault] could not be unlocked. Verify the KeePass database path, KeePass key file, and protected master password in the provider settings."
+        }
+    }
+}