feat: Add Exponential Histogram

[mwear]

Which problem is this PR solving?

This PR includes an implementation of the Exponential Histogram for Javascript. It is heavily based on the Golang Reference Implementation.

Fixes #3324

Short description of the changes

This PR contains the entire implementation of the Exponential Histogram, but can be considered in three parts. They are:

• The mapping functions, based on the IEEE 754 floating point standard, described at length in the spec
• The ExponentialHistogramAccumulation and ExponentialHistogramAggregation
• The interfaces and code necessary to transform and export the ExponentialHistogram to OTLP

Note: I will give a walkthrough of this PR at the JS SIG meeting on Dec 21.

Type of change

Please delete options that are not relevant.

• [x] New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• [x] Extensive unit testing. Many of the cases were borrowed from the Golang Reference implementation
• [x] End to end testing (exporting data via an OTel collector to a metric backend)

Checklist:

• [x] Followed the style guidelines of this project
• [x] Unit tests have been added
• [x] Documentation has been updated (there are docs in the source code, we'll likely need to do a pass on metrics docs at some point).

[codecov[bot]]

Codecov Report

Merging #3498 (46eecbb) into main (1c3af6c) will increase coverage by 0.21%. The diff coverage is 97.19%.

:exclamation: Current head 46eecbb differs from pull request most recent head e293cdd. Consider uploading reports for the commit e293cdd to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3498      +/-   ##
==========================================
+ Coverage   93.74%   93.95%   +0.21%     
==========================================
  Files         249      256       +7     
  Lines        7593     8057     +464     
  Branches     1582     1673      +91     
==========================================
+ Hits         7118     7570     +452     
- Misses        475      487      +12     

Impacted Files	Coverage Δ
...tal/packages/otlp-transformer/src/metrics/types.ts	100.00% <ø> (ø)
packages/sdk-metrics/src/export/MetricData.ts	100.00% <ø> (ø)
packages/sdk-metrics/src/view/Aggregation.ts	93.82% <55.55%> (-4.79%)	:arrow_down:
...trics/src/aggregator/exponential-histogram/util.ts	94.11% <94.11%> (ø)
...sdk-metrics/src/aggregator/ExponentialHistogram.ts	97.18% <97.18%> (ø)
...cs/src/aggregator/exponential-histogram/Buckets.ts	98.01% <98.01%> (ø)
.../packages/otlp-transformer/src/metrics/internal.ts	98.00% <100.00%> (+0.27%)	:arrow_up:
...r/exponential-histogram/mapping/ExponentMapping.ts	100.00% <100.00%> (ø)
.../exponential-histogram/mapping/LogarithmMapping.ts	100.00% <100.00%> (ø)
...ggregator/exponential-histogram/mapping/ieee754.ts	100.00% <100.00%> (ø)
... and 4 more

[mwear]

Based on the discussion at the SIG meeting earlier today, I split this PR into three parts. See:

• Part 1 - The mapping functions
• Part 2 - The accumulation and aggregator
• Part 3 - Wiring up export

I'll leave this draft PR open so folks can see the three parts combined.

[github-actions[bot]]

This PR is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 14 days.

[pichlermarc]

I'm closing this PR as all three parts (see below) have merged :tada:

• Part 1 - The mapping functions
• Part 2 - The accumulation and aggregator
• Part 3 - Wiring up export

Thank you again, @mwear, for putting in all the work and sticking with us during the reviews :slightly_smiling_face: