Cache Results of the Exists CQL Expression

[alexanderkiel]

Closes: #1051

[codecov]

Codecov Report

Attention: Patch coverage is 80.92255% with 335 lines in your changes missing coverage. Please review.

Project coverage is 94.74%. Comparing base (48942a8) to head (fa18fd8).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1796      +/-   ##
===========================================
- Coverage    96.20%   94.74%   -1.46%     
===========================================
  Files          271      282      +11     
  Lines        17353    18412    +1059     
  Branches       347      428      +81     
===========================================
+ Hits         16694    17445     +751     
- Misses         312      539     +227     
- Partials       347      428      +81     

Files	Coverage Δ
modules/cql/src/blaze/elm/compiler.clj	100.00% <100.00%> (ø)
.../cql/src/blaze/elm/compiler/clinical_operators.clj	100.00% <100.00%> (ø)
...ql/src/blaze/elm/compiler/library/resolve_refs.clj	100.00% <100.00%> (ø)
...ules/cql/src/blaze/elm/compiler/type_operators.clj	89.35% <100.00%> (+1.78%)	⬆️
modules/cql/src/blaze/elm/date_time.clj	93.23% <ø> (ø)
modules/cql/src/blaze/elm/expression.clj	100.00% <ø> (ø)
...ql/src/blaze/elm/expression/cache/bloom_filter.clj	100.00% <100.00%> (ø)
.../cql/src/blaze/elm/expression/cache/codec/by_t.clj	100.00% <100.00%> (ø)
.../cql/src/blaze/elm/expression/cache/codec/form.clj	100.00% <100.00%> (ø)
...s/cql/src/blaze/elm/expression/cache/protocols.clj	100.00% <100.00%> (ø)
... and 46 more

... and 3 files with indirect coverage changes