Add minimum token permissions for all github workflow files

[opentelemetrybot]

See open-telemetry/sig-security#148 for details.

Please check this PR carefully and watch out for any permission-related workflow failures after merging it.

cc @trask

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.65%. Comparing base (3968f74) to head (4befc80).
Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1655      +/-   ##
============================================
+ Coverage     68.64%   68.65%   +0.01%     
  Complexity     2854     2854              
============================================
  Files           425      425              
  Lines          8699     8699              
============================================
+ Hits           5971     5972       +1     
+ Misses         2728     2727       -1     

Flag	Coverage Δ
8.1	68.39% <ø> (+0.01%)	⬆️
8.2	68.56% <ø> (-0.04%)	⬇️
8.3	68.61% <ø> (+0.04%)	⬆️
8.4	68.56% <ø> (-0.05%)	⬇️
8.5	68.59% <ø> (-0.02%)	⬇️

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see 3 files with indirect coverage changes

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