feat: web metrics preserve data types, allow insecure tls, and make jsonPath optional

[jessesuen]

Resolves #728, #718, #717

1. When using jsonPath, the web metric always converted the result into a string. This is why the asFloat and asInt helpers were introduced, in to convert these strings into numbers so that mathematical comparison could be performed. This change preserves the original types so that asFloat and asInt are no longer necessary (as long as the original data types are numeric).

2. Previously, jsonPath was a required field. This change allows jsonPath to be omitted, in which case the entire body is the payload.

3. Added an insecure: true field that allows the web metric to disable TLS host verification when making HTTP requests.

[codecov-commenter]

Codecov Report

Merging #731 into master will decrease coverage by 0.47%.
The diff coverage is 38.75%.

@@            Coverage Diff             @@
##           master     #731      +/-   ##
==========================================
- Coverage   82.91%   82.44%   -0.48%     
==========================================
  Files          95       95              
  Lines        7926     7992      +66     
==========================================
+ Hits         6572     6589      +17     
- Misses        951      999      +48     
- Partials      403      404       +1     

Impacted Files	Coverage Δ
utils/evaluate/evaluate.go	56.86% <32.25%> (-38.98%)	⬇️
metricproviders/webmetric/webmetric.go	65.71% <61.11%> (-4.98%)	⬇️

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[khhirani]

LGTM