Pass int64 using Int64GetDatum when a Datum is required

[gayyappan]

int64 should be passed to functions that take a Datum parameter using Int64GetDatum.
Depending on the platform, postgres either passes int64 by value or allocs a pointer
to hold this value.
Without this change, we get SEGV on raspberry pi.

[codecov]

Codecov Report

Merging #1228 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1228      +/-   ##
==========================================
+ Coverage   92.56%   92.56%   +<.01%     
==========================================
  Files         107      107              
  Lines       13709    13710       +1     
==========================================
+ Hits        12690    12691       +1     
  Misses       1019     1019

Impacted Files	Coverage Δ
tsl/src/continuous_aggs/materialize.c	94.14% <ø> (ø)	⬆️
tsl/src/continuous_aggs/create.c	97.36% <100%> (ø)	⬆️
src/utils.c	85.42% <100%> (ø)	⬆️
tsl/test/src/test_continuous_aggs.c	95.83% <100%> (ø)	⬆️
src/loader/bgw_message_queue.c	91.6% <0%> (ø)	⬆️

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[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@7d30599). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master    #1228   +/-   ##
=========================================
  Coverage          ?   92.73%           
=========================================
  Files             ?      106           
  Lines             ?    13552           
  Branches          ?        0           
=========================================
  Hits              ?    12567           
  Misses            ?      985           
  Partials          ?        0

Impacted Files	Coverage Δ
tsl/src/continuous_aggs/materialize.c	94.14% <ø> (ø)
tsl/src/continuous_aggs/create.c	97.36% <100%> (ø)
tsl/test/src/test_continuous_aggs.c	95.83% <100%> (ø)

---

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