Remove quite a few array access code

[Licenser]

Pull request

Ensure we don't panic due to use of []

Description

using [] to access data can lead to rust panicing, we want to forbid this.

Checklist

• The RFC, if required, has been submitted and approved
• Any user-facing impact of the changes is reflected in docs.tremor.rs
• The code is tested
• Use of unsafe code is reasoned about in a comment

[codecov]

Codecov Report

Merging #574 (181e3d7) into main (cdb2bd2) will increase coverage by 0.02%.
The diff coverage is 81.07%.

@@            Coverage Diff             @@
##             main     #574      +/-   ##
==========================================
+ Coverage   80.49%   80.51%   +0.02%     
==========================================
  Files         101      101              
  Lines       13770    13868      +98     
==========================================
+ Hits        11084    11166      +82     
- Misses       2686     2702      +16     

Impacted Files	Coverage Δ
src/preprocessor/lines.rs	90.00% <0.00%> (ø)
src/source.rs	37.40% <0.00%> (ø)
tremor-pipeline/src/op/grouper/bucket.rs	90.65% <ø> (ø)
tremor-script/src/query.rs	65.45% <ø> (ø)
tremor-script/src/script.rs	80.39% <ø> (ø)
src/registry.rs	74.00% <50.00%> (-0.83%)	⬇️
src/preprocessor.rs	80.75% <55.55%> (-0.30%)	⬇️
tremor-pipeline/src/executable_graph.rs	84.94% <62.50%> (-0.06%)	⬇️
tremor-pipeline/src/op/trickle/script.rs	72.72% <62.50%> (-1.05%)	⬇️
tremor-script/src/std_lib/stats.rs	62.60% <63.63%> (ø)
... and 23 more

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