Rewrite precise-code-intel-bundle-manager in Go

[efritz]

This is a rewrite of the precise-code-intel-bundle-manager in Go. This does not change the current entrypoints as we're not ready to switch to the new code yet. I am planning on manually testing requests against the old and new servers to ensure the behavior is the same during usage. A follow-up PR(s) will remove the old code and switch to the new code in build and deployment environments.

This new code is fairly well tested (database: 79.2% coverage, janitor: 62.4% coverage, and types: 79.0%). The server code will be more fully tested before it replaces the existing TypeScript code.

This new code needs to emit metric, add tracing to requests, and wrap errors properly before being considered ready for production.

Opening PR now for discussion as it's a large chunk of code. This effort is tracked in #9964.

[codecov]

Codecov Report

Merging #9586 into master will increase coverage by 0.20%.
The diff coverage is 65.15%.

@@            Coverage Diff             @@
##           master    #9586      +/-   ##
==========================================
+ Coverage   42.74%   42.95%   +0.20%     
==========================================
  Files        1348     1354       +6     
  Lines       74083    74693     +610     
  Branches     6651     6651              
==========================================
+ Hits        31668    32081     +413     
- Misses      39562    39692     +130     
- Partials     2853     2920      +67     

Flag	Coverage Δ
#unit	42.95% <65.15%> (+0.20%)	⬆️

Impacted Files	Coverage Δ
enterprise/internal/campaigns/syncer.go	79.65% <ø> (ø)
internal/extsvc/bitbucketserver/events.go	0.00% <0.00%> (ø)
internal/httpcli/client.go	38.88% <ø> (ø)
internal/conf/conf.go	15.96% <40.00%> (-0.28%)	⬇️
...e-intel-bundle-manager/internal/janitor/janitor.go	51.02% <51.02%> (ø)
enterprise/internal/campaigns/webhooks.go	26.32% <52.27%> (+3.77%)	⬆️
...intel-bundle-manager/internal/database/database.go	61.23% <61.23%> (ø)
...de-intel-bundle-manager/internal/database/cache.go	72.72% <72.72%> (ø)
...e-intel-bundle-manager/internal/types/unmarshal.go	76.72% <76.72%> (ø)
cmd/gitserver/server/cleanup.go	67.94% <100.00%> (ø)
... and 11 more

[unknwon]

I haven't done reviewing the PRs, just some notes (for discussions) on skimming the files:

1. Is it too aggressive to log.Fatal for missing config values? Any chance we could just fall back to use a default? NVM, I see we've been using it in many places.
2. We started using cmp.Diff instead of reflect.DeepEqual in new code, examples: https://sourcegraph.com/search?q=repo:%5Egithub%5C.com/sourcegraph/sourcegraph%24+cmp.Diff&patternType=literal
3. The directory name for test data we're currently using is "testdata" (without dash).
4. Would be nice to have a list of non-go files and how they will be used later, it isn't obvious to me so far.
5. Nice examples with all the ^^^^^s 👍

[unknwon]

Submitting my partial reviews so number of comments aren't overwhelming. Very enjoyable piece of code though!

[unknwon]

Nice! Approve to unblock.

[keegancsmith]

LGTM. I didn't deeply review due to size. Rather just took a high level view over it to see anything that stood out. So sorry for only finding nits :) Nice work!