Optimize VFS::touch and fix defects and race conditions.

[teo-tsirpanis]

SC-53188
SC-53189
SC-54494

This PR updates the implementations of VFS::touch for Azure, GCS and Windows to improve performance and fix race conditions:

• On Azure we remove checking if the blob exists, and instead use a single conditional request to upload an empty blob if it does not already exist. This reduces round-trips and fixes race conditions if the blob was created between the existence check and the upload.
• GCS did not even have an existence check, which means that the behavior of touch was incorrect and always overwrote the file. This was fixed by adding a request precondition.
• On Windows the existence check was removed. We were already doing the right thing and opened the file with CREATE_NEW, but did not mask failures with ERROR_FILE_EXISTS status code. We fix this.

Additionally, the documentation of tiledb_vfs_touch was updated to mention that the file is created only if it does not exist, matching existing behavior in most VFS implmentations, and the expectations from the touch command.

Testing coverage was added.

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TYPE: BUG
DESC: Fixed tiledb_vfs_touch to not overwrite existing files on GCS.

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TYPE: BUG
DESC: Fixed tiledb_vfs_touch to not overwrite existing files or fail on Azure and Windows respectively, under race conditions.

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TYPE: C_API
DESC: Update documentation of tiledb_vfs_touch to specify that existing files are not overwritten, matching the current behavior.