refactor: remove sscan and sget command in tablet client

[frazie]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  deletion of unused functions

• What is the current behavior? (You can also link to an open issue here)

• What is the new behavior (if this is a feature change)?

[codecov]

Codecov Report

Merging #1886 (cb2e890) into main (50d0699) will decrease coverage by 0.08%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##               main    #1886      +/-   ##
============================================
- Coverage     75.76%   75.68%   -0.09%     
  Complexity      347      347              
============================================
  Files           613      613              
  Lines        117018   117018              
  Branches       1024     1024              
============================================
- Hits          88663    88567      -96     
- Misses        28146    28242      +96     
  Partials        209      209              

Impacted Files	Coverage Δ
...s/query_response_time/deploy_query_response_time.h	81.25% <0.00%> (-18.75%)	⬇️
src/log/status.h	70.83% <0.00%> (-12.50%)	⬇️
src/sdk/db_sdk.cc	62.58% <0.00%> (-6.58%)	⬇️
...atistics/query_response_time/query_response_time.h	78.26% <0.00%> (-4.35%)	⬇️
src/replica/replicate_node.cc	74.30% <0.00%> (-3.92%)	⬇️
.../query_response_time/deploy_query_response_time.cc	97.10% <0.00%> (-2.90%)	⬇️
src/log/log_reader.cc	76.47% <0.00%> (-2.65%)	⬇️
src/rpc/rpc_client.h	89.18% <0.00%> (-1.36%)	⬇️
src/tablet/tablet_impl.cc	59.34% <0.00%> (-0.47%)	⬇️
src/catalog/client_manager.cc	42.20% <0.00%> (-0.29%)	⬇️
... and 4 more

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[github-actions]

SDK Test Report

  75 files    75 suites   7m 59s ⏱️
163 tests 161 ✔️ 2 💤 0 ❌
204 runs  202 ✔️ 2 💤 0 ❌

Results for commit cb2e890.

[github-actions]

Linux Test Report

       57 files       187 suites   1h 2m 1s ⏱️
  8 503 tests   8 499 ✔️ 4 💤 0 ❌
12 489 runs  12 485 ✔️ 4 💤 0 ❌

Results for commit cb2e890.

[tobegit3hub]

LGTM