feat: Improve links to meeting tools from group pages

[jennifer-richards]

Fixes #4738. Fixes both views mentioned in the ticket.

On the group meeting page (/wg/oauth/meetings), the session buttons were included for each entry, but the session_buttons_include.html template required that now be set in the rendering context. To fix this, I've created a template tag that allows a template to get timezone.now() with {% get_now as now %} instead of relying on the view to pass it in.

For the meeting session page (/meeting/115/session/oauth), I've added a block for each session that shows the same links generated by the session_buttons_include.html, excluding a few that are redundant against what's already present. I've also updated this to use the get_now tag.

[codecov]

Codecov Report

Merging #5130 (7461ce5) into main (e280b25) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #5130      +/-   ##
==========================================
+ Coverage   88.50%   88.51%   +0.01%     
==========================================
  Files         295      295              
  Lines       40015    40018       +3     
==========================================
+ Hits        35415    35423       +8     
+ Misses       4600     4595       -5     

Impacted Files	Coverage Δ
ietf/ietfauth/utils.py	92.85% <ø> (ø)
ietf/meeting/views.py	90.70% <ø> (ø)
ietf/context_processors.py	68.96% <100.00%> (+3.58%)	⬆️
ietf/secr/sreq/views.py	91.16% <100.00%> (ø)
ietf/utils/text.py	85.97% <0.00%> (-0.61%)	⬇️
ietf/nomcom/utils.py	91.30% <0.00%> (-0.25%)	⬇️
ietf/doc/views_search.py	88.81% <0.00%> (ø)
ietf/utils/pipe.py	86.95% <0.00%> (+4.34%)	⬆️
ietf/utils/templatetags/textfilters.py	100.00% <0.00%> (+14.63%)	⬆️

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