bluetooth: SM: Add security request packet

[antoniovazquezblanco]

Checklist:

• If you are new to Scapy: I have checked CONTRIBUTING.md (esp. section submitting-pull-requests)
• I squashed commits belonging together
• I added unit tests or explained why they are not relevant
• I executed the regression tests (using cd test && ./run_tests or tox)
• If the PR is still not finished, please create a Draft Pull Request

One more Bluetooth packet to the collection!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.20%. Comparing base (0648c0d) to head (dc4167d).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4732   +/-   ##
=======================================
  Coverage   82.20%   82.20%           
=======================================
  Files         361      361           
  Lines       87195    87199    +4     
=======================================
+ Hits        71679    71683    +4     
  Misses      15516    15516           

Files with missing lines	Coverage Δ
scapy/layers/bluetooth.py	90.50% <100.00%> (+0.03%)	⬆️

... and 4 files with indirect coverage changes

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