fix: surface original stack trace and message with errors

[JustinBeckwith]

Fixes #643. This PR looks for multiple instances where context for exceptions could be lost. The two primary types of cases here are:

1. Completely overwriting the error message but retaining the stack trace
2. Catching, and throwing an entirely new error with the original context lost

Instead, we always make sure to re-throw the original error, and consistently pin the original error message to the tail of the new message.

[codecov]

Codecov Report

Merging #651 into master will decrease coverage by 0.14%.
The diff coverage is 75%.

@@            Coverage Diff             @@
##           master     #651      +/-   ##
==========================================
- Coverage   88.39%   88.25%   -0.15%     
==========================================
  Files          18       18              
  Lines         784      783       -1     
  Branches       86       84       -2     
==========================================
- Hits          693      691       -2     
- Misses         79       81       +2     
+ Partials       12       11       -1

Impacted Files	Coverage Δ
src/auth/computeclient.ts	93.93% <100%> (ø)	⬆️
src/auth/oauth2client.ts	86.45% <55.55%> (-0.24%)	⬇️
src/auth/googleauth.ts	91.28% <85.71%> (-0.18%)	⬇️

---

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[codecov]

Codecov Report

Merging #651 into master will decrease coverage by 0.14%.
The diff coverage is 75%.

@@            Coverage Diff             @@
##           master     #651      +/-   ##
==========================================
- Coverage   88.26%   88.12%   -0.15%     
==========================================
  Files          18       18              
  Lines         784      783       -1     
  Branches       86       84       -2     
==========================================
- Hits          692      690       -2     
- Misses         80       82       +2     
+ Partials       12       11       -1

Impacted Files	Coverage Δ
src/auth/computeclient.ts	93.93% <100%> (ø)	⬆️
src/auth/oauth2client.ts	86.45% <71.42%> (-0.24%)	⬇️
src/auth/googleauth.ts	90.76% <75%> (-0.19%)	⬇️

---

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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