add migration guide for 3.x to 4.x

[rochdev]

What does this PR do?

Add migration guide for 3.x to 4.x.

Motivation

With 4.0 around the corner, we need a migration guide for upgrading from 3.x.

[github-actions]

Overall package size

Self size: 4.11 MB
Deduped: 58.24 MB
No deduping: 58.29 MB

Dependency sizes

name	version	self size	total size
@datadog/pprof	2.2.1	14.24 MB	15.12 MB
@datadog/native-iast-taint-tracking	1.4.1	14.85 MB	14.86 MB
@datadog/native-appsec	3.1.0	13.31 MB	13.32 MB
protobufjs	7.1.2	2.76 MB	6.55 MB
@datadog/native-iast-rewriter	2.0.1	2.09 MB	2.1 MB
@datadog/native-metrics	2.0.0	898.77 kB	1.3 MB
opentracing	0.14.7	194.81 kB	194.81 kB
semver	7.3.8	88.2 kB	118.6 kB
@datadog/sketches-js	2.1.0	109.9 kB	109.9 kB
lodash.sortby	4.7.0	75.76 kB	75.76 kB
lru-cache	7.14.0	74.95 kB	74.95 kB
ipaddr.js	2.0.1	59.52 kB	59.52 kB
ignore	5.2.0	48.87 kB	48.87 kB
import-in-the-middle	1.3.5	34.34 kB	38.81 kB
istanbul-lib-coverage	3.2.0	29.34 kB	29.34 kB
retry	0.10.1	27.44 kB	27.44 kB
lodash.uniq	4.5.0	25.01 kB	25.01 kB
limiter	1.1.5	23.17 kB	23.17 kB
lodash.kebabcase	4.1.1	17.75 kB	17.75 kB
lodash.pick	4.4.0	16.33 kB	16.33 kB
node-abort-controller	3.0.1	14.33 kB	14.33 kB
crypto-randomuuid	1.0.0	11.18 kB	11.18 kB
diagnostics_channel	1.1.0	7.07 kB	7.07 kB
path-to-regexp	0.1.7	6.78 kB	6.78 kB
koalas	1.0.2	6.47 kB	6.47 kB
methods	1.1.2	5.29 kB	5.29 kB
module-details-from-path	1.0.3	4.47 kB	4.47 kB

_{🤖 This report was automatically generated by heaviest-objects-in-the-universe}

[codecov]

Codecov Report

Merging #3137 (286ba98) into master (4e7da80) will increase coverage by 0.22%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3137      +/-   ##
==========================================
+ Coverage   87.15%   87.37%   +0.22%     
==========================================
  Files         316      326      +10     
  Lines       11585    11845     +260     
  Branches       33       33              
==========================================
+ Hits        10097    10350     +253     
- Misses       1488     1495       +7     

see 10 files with indirect coverage changes

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[juan-fernandez]

looks good from ci visibility's perspective. Only two minor comments

[pr-commenter]

Benchmarks

Comparing candidate commit 286ba98 in PR branch migration-3-to-4 with baseline commit 4e7da80 in branch master.

Found 0 performance improvements and 1 performance regressions! Performance is the same for 670 metrics, 37 unstable metrics.

scenario:plugin-graphql-control-14

• 🟥 execution_time [+0.356s; +0.559s] or [+13.514%; +21.254%]