Fix: Expand multi-value template variables in prefixPath into multiple paths (#109)

* Expand multi-value template variables in prefixPath into multiple paths

Fix two issues with variable expansion in Grafana 11.4 (Scenes architecture):

1. Replace templateSrv.containsTemplate() with regex-based detection.
   In Grafana 11.4's Scenes mode, containsTemplate() returns false for
   ${var} syntax even when the variable exists. Using a regex pattern
   ensures reliable detection regardless of Grafana version.

2. Process prefixPath expansion for queries without sqlType field.
   Previously only queries with sqlType === 'SQL: Full Customized' were
   processed. Queries provisioned via JSON (without explicit sqlType)
   were silently skipped.

The expansion logic now:
- Detects variables via regex pattern /\$\{(\w+)(?::[^}]*)?\}|\\b/
- Resolves values from scopedVars first, then falls back to getVariables()
- Handles $__all by expanding to all non-$__all options
- Supports both single-value and multi-value (array) variables
- Fully backward-compatible: literal paths pass through unchanged

Closes #108

* Address review: handle $__all in scopedVars and safer fallback

- When scopedVars provides $__all, expand using options list instead of
  treating it as a literal path segment
- When variable cannot be resolved, fallback to replace() on the whole
  path (preserving prior behavior) instead of only replacing the token
- Add tests for both cases

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Co-authored-by: xiangdong huang <hxd@timecho.com>