Fix int overflow issue for progress

[var77]

As the progress was int32, the progress was overflowing if index is bigger than ~2GB.

[codecov]

Codecov Report

Merging #186 (545c4ae) into main (29af187) will not change coverage.
The diff coverage is 100.00%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #186   +/-   ##
=======================================
  Coverage   83.09%   83.09%           
=======================================
  Files          17       17           
  Lines        1201     1201           
  Branches      256      256           
=======================================
  Hits          998      998           
  Misses         81       81           
  Partials      122      122           

Files	Coverage Δ
src/hnsw/external_index.c	91.09% <100.00%> (ø)

[github-actions]

Benchmarks

metric	old	new	pct change
recall (after create)	0.740	0.740	-
recall (after insert)	0.774	0.758	-2.07%
select bulk tps	221.794	236.280	+6.53%
select bulk latency (ms)	34.222	30.683	-10.34%
select bulk latency (stddev ms)	10.459	13.949	+33.37%
create latency (ms)	1458.342	1565.197	+7.33%
insert bulk tps	13.953	14.122	+1.21%
insert bulk latency (ms)	71.652	70.799	-1.19%
insert bulk latency (stddev ms)	6.077	2.105	-65.36%
disk usage (bytes)	6348800.000	6348800.000	-