doc: add tls.cert_chain_len docs

[jmtaylor90]

Make sure these boxes are signed before submitting your Pull Request -- thank you.

• I have read the contributing guide lines at https://docs.suricata.io/en/latest/devguide/codebase/contributing/contribution-process.html
• I have signed the Open Information Security Foundation contribution agreement at https://suricata.io/about/contribution-agreement/
• I have updated the user guide (in doc/userguide/) to reflect the changes made (if applicable)

Link to redmine ticket:

https://redmine.openinfosecfoundation.org/issues/6386

Describe changes:

Provide values to any of the below to override the defaults.

To use a pull request use a branch name like pr/N where N is the
pull request number.

Alternatively, SV_BRANCH may also be a link to an
OISF/suricata-verify pull-request.

SV_REPO=
SV_BRANCH=
SU_REPO=
SU_BRANCH=
LIBHTP_REPO=
LIBHTP_BRANCH=

[jmtaylor90]

The code work was done under https://redmine.openinfosecfoundation.org/issues/5191 / 682e2a0 it looks like the documentation was missed. So this is the associated doc work. Do we need a new redmine for this?

[codecov]

Codecov Report

Merging #9569 (9db1c3f) into master (9157070) will decrease coverage by 0.01%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #9569      +/-   ##
==========================================
- Coverage   82.20%   82.19%   -0.01%     
==========================================
  Files         968      968              
  Lines      274275   274275              
==========================================
- Hits       225461   225449      -12     
- Misses      48814    48826      +12     

Flag	Coverage Δ
fuzzcorpus	64.05% <ø> (+<0.01%)	⬆️
suricata-verify	60.92% <ø> (-0.03%)	⬇️
unittests	62.87% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

[inashivb]

The code work was done under https://redmine.openinfosecfoundation.org/issues/5191 / 682e2a0 it looks like the documentation was missed. So this is the associated doc work. Do we need a new redmine for this?

Looking at other Documentation tickets, I'd say yes. Preferably as a subtask of https://redmine.openinfosecfoundation.org/issues/5182

[jmtaylor90]

The code work was done under https://redmine.openinfosecfoundation.org/issues/5191 / 682e2a0 it looks like the documentation was missed. So this is the associated doc work. Do we need a new redmine for this?

Looking at other Documentation tickets, I'd say yes. Preferably as a subtask of https://redmine.openinfosecfoundation.org/issues/5182

Thanks! It appears I don't have the redmine permissions to add a subtask to that ticket so I created the new ticket and added it as a related issue to 5182.

[jufajardini]

Doc changes look good, thanks for catching this :)

Considering now we have a ticket for it, would be good to have it on the commit message :P

[jmtaylor90]

continued in #9597