Deprecate exposed-bgp check by a Nuclei template

[danfaizer]

The goal of this PR is deprecate vulcan-exposed-bgp check in favour of vulcan-nuclei check by providing custom Nuclei template.

Templates added:

• BGP Detect

Test the template:

# Nuclei binary is required.

bash ./cmd/vulcan-nuclei/tests/bgp.bash &; \
nuclei \
   -t ./cmd/vulcan-nuclei/templates/network/detection/bgp-detect.yaml \
   -u localhost