Fix possible corruption when iterating metric result [MOD-5791]

[alonre24]

Addressing #3841

Describe the changes in the pull request

In RSIndexResult_IterateOffsets - we didn't check if the result is of type metric, which led to possible corruption.

Mark if applicable

• This PR introduces API changes
• This PR introduces serialization changes

[codecov]

Codecov Report

Patch coverage: 66.66% and project coverage change: -0.02% ⚠️

Comparison is base (88b60ad) 82.82% compared to head (9087345) 82.80%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3854      +/-   ##
==========================================
- Coverage   82.82%   82.80%   -0.02%     
==========================================
  Files         192      192              
  Lines       32575    32575              
==========================================
- Hits        26979    26975       -4     
- Misses       5596     5600       +4     

Files Changed	Coverage Δ
src/offset_vector.c	82.07% <ø> (ø)
src/index_result.c	85.47% <66.66%> (ø)

... and 3 files with indirect coverage changes

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[GuyAv46]

LGTM

[DvirDukhan]

/backport

[github-actions]

Successfully created backport PR for 2.8:

• [2.8] Fix possible corruption when iterating metric result [MOD-5791] #3859

[github-actions]

Successfully created backport PR for 2.10:

• [2.10] Fix possible corruption when iterating metric result [MOD-5791] #3860