[bug] Avoid redundant cache loading (#7741)

Issue: #7002 

### Brief Summary

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### <samp>🤖 Generated by Copilot at f2ee059</samp>

Improve kernel compilation manager efficiency by avoiding redundant
cache loading.
### Walkthrough

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### <samp>🤖 Generated by Copilot at f2ee059</samp>

* Add a check for existing kernel data to avoid redundant loading
([link](https://github.com/taichi-dev/taichi/pull/7741/files?diff=unified&w=0#diff-b7662dbf5bcf20f4b99048f4f2405316c0ba037c0722273522efaad72d256ef0L219-R228))

taichi/compilation_manager/kernel_compilation_manager.cpp

@@ -216,7 +216,11 @@ const CompiledKernelData *KernelCompilationManager::try_load_cached_kernel(
     auto iter = kernels.find(kernel_key);
     if (iter != kernels.end()) {
       auto &k = iter->second;
-      if (auto loaded = load_ckd(kernel_key, arch)) {
+      if (k.compiled_kernel_data) {
+        TI_DEBUG("Create kernel '{}' from cache (key='{}')",
+                 kernel_def.get_name(), kernel_key);
+        return k.compiled_kernel_data.get();
+      } else if (auto loaded = load_ckd(kernel_key, arch)) {
         TI_DEBUG("Create kernel '{}' from cache (key='{}')",
                  kernel_def.get_name(), kernel_key);
         TI_ASSERT(loaded->arch() == arch);