Introduce systemtest/cmd/fleetctl

[axw]

Motivation/summary

Add a basic CLI for listing Fleet package policies, and updating their config vars, for use in development and testing. This may be useful for manipulating config vars that are not shown in the APM integration policy editor.

Listing policies: fleetctl -u <kibana_url> list-policies

Updating vars: fleetctl -u <kibana_url> set-policy-var <ID> tail_sampling_storage_limit=30MB

Checklist

~- [ ] Update CHANGELOG.asciidoc~ ~- [ ] Update package changelog.yml (only if changes to apmpackage have been made)~ ~- [ ] Documentation has been updated~

How to test these changes

N/A

Related issues

None

[mergify[bot]]

This pull request does not have a backport label. Could you fix it @axw? 🙏 To fixup this pull request, you need to add the backport labels for the needed branches, such as:

• backport-7.x is the label to automatically backport to the 7.x branch.
• backport-7./d is the label to automatically backport to the 7./d branch. /d is the digit

NOTE: backport-skip has been added to this pull request.

[apmmachine]

:green_heart: Build Succeeded

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Build stats

• Start Time: 2022-08-14T12:41:19.284+0000

• Duration: 24 min 39 sec

Test stats :test_tube:

Test	Results
Failed	0
Passed	137
Skipped	1
Total	138

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[apmmachine]

:books: Go benchmark report

Diff with the main branch

name                                                            old time/op    new time/op    delta
pkg:github.com/elastic/apm-server/internal/agentcfg goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/internal/decoder goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/internal/model/modelindexer goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/internal/processor/stream goos:linux goarch:amd64
BackendProcessor-12                                               0.00ns ±25%    0.00ns ±43%  -47.56%  (p=0.008 n=5+5)
pkg:github.com/elastic/apm-server/internal/publish goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/x-pack/apm-server/aggregation/spanmetrics goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/x-pack/apm-server/aggregation/txmetrics goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/x-pack/apm-server/sampling goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/x-pack/apm-server/sampling/eventstorage goos:linux goarch:amd64
WriteTransaction/json_codec_big_tx-12                             5.05µs ±21%    4.65µs ± 1%   -7.99%  (p=0.016 n=5+4)
ReadEvents/json_codec/100_events-12                                684µs ± 0%     695µs ± 1%   +1.57%  (p=0.016 n=5+5)
ReadEvents/json_codec_big_tx/0_events-12                           335ns ± 6%     307ns ± 3%   -8.36%  (p=0.008 n=5+5)
IsTraceSampled/unsampled-12                                       79.0ns ± 1%    77.9ns ± 1%   -1.42%  (p=0.032 n=5+5)

name                                                            old alloc/op   new alloc/op   delta
pkg:github.com/elastic/apm-server/internal/agentcfg goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/internal/decoder goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/internal/model/modelindexer goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/internal/processor/stream goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/internal/publish goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/x-pack/apm-server/aggregation/spanmetrics goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/x-pack/apm-server/aggregation/txmetrics goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/x-pack/apm-server/sampling goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/x-pack/apm-server/sampling/eventstorage goos:linux goarch:amd64

name                                                            old allocs/op  new allocs/op  delta
pkg:github.com/elastic/apm-server/internal/agentcfg goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/internal/decoder goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/internal/model/modelindexer goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/internal/processor/stream goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/internal/publish goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/x-pack/apm-server/aggregation/spanmetrics goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/x-pack/apm-server/aggregation/txmetrics goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/x-pack/apm-server/sampling goos:linux goarch:amd64
pkg:github.com/elastic/apm-server/x-pack/apm-server/sampling/eventstorage goos:linux goarch:amd64

report generated with https://pkg.go.dev/golang.org/x/perf/cmd/benchstat