Clean up some switch statements and if chains

[jeltz]

In tde_keyring.c we do a lot of switching on the keyring type, some of it which could be done in a slightly nicer way.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 40.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 78.42%. Comparing base (e355f38) to head (0220117).

❌ Your project status has failed because the head coverage (78.42%) is below the target coverage (90.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@                  Coverage Diff                  @@
##           TDE_REL_17_STABLE     #273      +/-   ##
=====================================================
+ Coverage              78.34%   78.42%   +0.08%     
=====================================================
  Files                     22       22              
  Lines                   2484     2480       -4     
  Branches                 391      388       -3     
=====================================================
- Hits                    1946     1945       -1     
+ Misses                   462      459       -3     
  Partials                  76       76              

Components	Coverage Δ
access	79.35% <ø> (ø)
catalog	86.51% <40.00%> (+0.27%)	⬆️
common	92.50% <ø> (ø)
encryption	71.90% <ø> (ø)
keyring	72.07% <ø> (ø)
src	53.79% <ø> (ø)
smgr	98.01% <ø> (ø)
transam	∅ <ø> (∅)

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