committed binary file: blackbox_exporter

instead of copying from the repository, download and install it.

```
RUN wget https://github.com/prometheus/blackbox_exporter/releases/download/v0.15.1/blackbox_exporter-0.15.1.linux-amd64.tar.gz -O /tmp/blackbox_exporter.tar.gz && \
tar -xz -f /tmp/blackbox_exporter.tar.gz --strip-components 1 -C /bin blackbox_exporter-0.15.1.linux-amd64/blackbox_exporter && \
rm -rf /tmp/blackbox_exporter.tar.gz
```

Find the Dockerfile that currently copies the blackbox_exporter binary from the repository. Start by checking how that binary is added to the image, then use the issue's release URL and installation commands as the target behavior. Done means the image downloads and installs version 0.15.1 during its build without copying the binary from the repository.

Written by the indexing model from the issue text.