chore: improve performance for basickv lookup

[zz-jason]

What's changed and how does it work?

• rename Worker to WorkerContext
• support optimistic lookup for basic kv, close Support optimistic lookup for basic kv #120
• move std::function objects to avoid unnecessary memory allocation
• manage CRManager with raw pointer to avoid overhead of std::unique_ptr

[codecov]

Codecov Report

Attention: Patch coverage is 67.01571% with 63 lines in your changes missing coverage. Please review.

Project coverage is 56.99%. Comparing base (d5e3d71) to head (3c9e1a4).
Report is 1 commits behind head on main.

Files	Patch %	Lines
src/btree/TransactionKV.cpp	57.14%	13 Missing and 2 partials ⚠️
src/leanstore-c/leanstore-c.cpp	45.83%	12 Missing and 1 partial ⚠️
src/btree/Tuple.cpp	0.00%	9 Missing ⚠️
src/btree/BasicKV.cpp	71.42%	5 Missing and 1 partial ⚠️
src/concurrency/ConcurrencyControl.cpp	68.42%	1 Missing and 5 partials ⚠️
include/leanstore/btree/ChainedTuple.hpp	33.33%	3 Missing and 1 partial ⚠️
src/btree/ChainedTuple.cpp	50.00%	1 Missing and 2 partials ⚠️
...de/leanstore/buffer-manager/GuardedBufferFrame.hpp	83.33%	0 Missing and 2 partials ⚠️
src/LeanStore.cpp	87.50%	1 Missing and 1 partial ⚠️
include/leanstore/btree/TransactionKV.hpp	0.00%	1 Missing ⚠️
... and 2 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #121      +/-   ##
==========================================
- Coverage   62.80%   56.99%   -5.81%     
==========================================
  Files         119       97      -22     
  Lines        9015     7044    -1971     
  Branches     3471     3113     -358     
==========================================
- Hits         5662     4015    -1647     
+ Misses       2952     2629     -323     
+ Partials      401      400       -1     

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