Resolve a threading issue with secrets; Handle SecretStore vaults better with inbuilt defaults; Write documentation for SecretStore vaults

[Badgerati]

Description of the Change

• Resolves a threading issue with secrets and vaults by creating a Lockable per vault, and adding Lock-PodeObject wrappers to Get, Set, Read, Update, Remove, and Unlock functions.
• Adds inbuilt defaults when using the SecretStore secret vault provider, so it can be more easily used.
• Adds documentation for SecretStore, and flags that -UnlockSecret is mandatory.

Related Issue

Resolves #1180
Resolves #1250

Examples

Start-PodeServer -Threads 2 {
    Add-PodeEndpoint -Address * -Port 8080 -Protocol Http

    # register the vault
    Register-PodeSecretVault `
        -Name 'ExampleVault' `
        -ModuleName 'Microsoft.PowerShell.SecretStore' `
        -UnlockSecret 'Sup3rSecur3Pa$$word!'

    # set a secret in the local vault
    Set-PodeSecret -Key 'example' -Vault 'ExampleVault' -InputObject 'hello, world!'

    # mount the "example" secret from local vault, making it accessible via $secret:example
    Mount-PodeSecret -Name 'example' -Vault 'ExampleVault' -Key 'example'

    # retrieve the secret in a route
    Add-PodeRoute -Method Get -Path '/' -ScriptBlock {
        Write-PodeJsonResponse @{ Value = $secret:example }
    }

    # update the secret in a route
    Add-PodeRoute -Method Post -Path '/' -ScriptBlock {
        $secret:example = $WebEvent.Data.Value
    }
}