…lated

PR #63955 introduced `loadedRawVars` tracking in `doLoad()`. Its check
`!isset($_ENV[$name])` was meant to protect host-provided environment
variables from being processed by `resolveLoadedVars()`. However, with
PHP's default `variables_order = "GPCS"` (no `E`), OS-provided env vars
are placed in $_SERVER but not in $_ENV when PHP starts.

As a result, an externally provided value like `abc$def` was added to
`loadedRawVars`, and then `resolveLoadedVars()` interpreted the literal
`$` as a variable reference and truncated the value to `abc`.

Mirror the existing behavior of `populate()` which already considers
$_SERVER as a source of pre-existing env vars, so externally provided
values are correctly recognized regardless of `variables_order`.

* 6.4:
  [Scheduler] Make debug:scheduler test independent of terminal width
  [Messenger] Fix ErrorDetailsStampTest after dropping trace args from normalization
  [Scheduler] Use stored checkpoint as base date for debug:scheduler
  [Messenger] Drop trace args from FlattenException normalization
  [HttpKernel] Use backend-handled request for terminate listeners in HttpCache
  [WebProfilerBundle] Don’t try to access `RawMessage::$headers`
  [Security] Clarify AbstractToken's role-name decoupling and simplify ContextListener
  [Dotenv] Don't truncate OS env vars containing $ when $_ENV is unpopulated