Refactor syncWithPrimary and replicaTryPartialResynchronization

[nitaicaro]

In continuation to #945

syncWithPrimary:

• Refactored returns and memory frees to single goto error/goto ok label
• Refactored repl_state state machine from if-else format to switch-case format
• Besides changing the repl_state, all state machine logic moved to helper functions

replicaTryPartialResynchronization:
This function was performing two different jobs based on the value of the read_reply argument -

• read_reply == 0: Sends the PSYNC command to the primary server.
• read_reply == 1: Reads and processes the reply to the PSYNC command.

This change simplifies the logic by clearly separating the writing and reading stages of the PSYNC process.

The PR was split into individual commits for easy review.

[codecov]

Codecov Report

Attention: Patch coverage is 86.98630% with 19 lines in your changes missing coverage. Please review.

Project coverage is 70.85%. Comparing base (9f4503c) to head (a071443).
Report is 2 commits behind head on unstable.

Files with missing lines	Patch %	Lines
src/replication.c	86.98%	19 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable    #1476      +/-   ##
============================================
- Coverage     70.86%   70.85%   -0.02%     
============================================
  Files           119      119              
  Lines         64859    64882      +23     
============================================
+ Hits          45963    45972       +9     
- Misses        18896    18910      +14     

Files with missing lines	Coverage Δ
src/replication.c	87.60% <86.98%> (+0.07%)	⬆️

... and 11 files with indirect coverage changes