Adjust global logger default level to align with config.logging_level when no context is created.

[kounelisagis]

This PR updates the default logging level of global_logger based on the TILEDB_VERBOSE flag. This ensures that the global logger's default logging level aligns with config.logging_level, even before a Context is created. Previously, the level was unconditionally set to Logger::Level::ERR, regardless of the flag.

If a Context was created before the global logger, the logging level was correctly set:

TileDB/tiledb/sm/storage_manager/context.cc

Line 228 in 7296b27

global_logger().set_level(static_cast<Logger::Level>(level));

However, if global_logger was used before any Context was created, the logging level was incorrectly set. This behavior was noticed in context-free C APIs that use api_entry_error. When these APIs were called before a Context was created, log messages appeared after calling LOG_ERROR(const std::string& msg), even if the TILEDB_VERBOSE flag was not set.

Closes CORE-269

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Reproduction

One such C API is tiledb_config_load_from_file. When the filename argument is set to NULL, it throws a CAPIStatusException. Below is a script demonstrating this behavior: when the line that allocated the context is included, nothing appears on the user's screen using the default config.logging_level value. However, if that line is commented out, a log message appears like the following: [2025-06-20 20:04:08.442] [Process: 85057] [error] [1750439048442019000-Global] C API: Cannot load from file; null filename

#include <tiledb/tiledb.h>

int main() {
  tiledb_ctx_t* ctx;
  tiledb_ctx_alloc(NULL, &ctx); // Comment this line to see the differt behavior

  tiledb_config_t* config;
  tiledb_error_t* error = NULL;
  tiledb_config_alloc(&config, &error);
  tiledb_config_load_from_file(config, NULL, &error);

  return 0;
}

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TYPE: IMPROVEMENT
DESC: Adjust global logger default level to align with config.logging_level when no context is created.