Oracles: use BoundedVec for feed values

[lemunozm]

Fixes #924

[codecov-commenter]

Codecov Report

Merging #925 (c9faa55) into master (0482bf2) will increase coverage by 0.08%.
The diff coverage is 100.00%.

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@@            Coverage Diff             @@
##           master     #925      +/-   ##
==========================================
+ Coverage   78.24%   78.32%   +0.08%     
==========================================
  Files         105      105              
  Lines       10627    10669      +42     
==========================================
+ Hits         8315     8357      +42     
  Misses       2312     2312              

Impacted Files	Coverage Δ
oracle/src/mock.rs	100.00% <ø> (ø)
oracle/src/lib.rs	78.57% <100.00%> (ø)
oracle/src/tests.rs	100.00% <100.00%> (ø)

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