Upgrade to Golang 1.16.4

[ph]

Upgrade to Golang 1.16.2:

• Update crossbuild images Update to Go 1.16.3 golang-crossbuild#82
• Update Beats to 1.16.2
• Update Fleet-Server
• Ping APM-Server
• Update macOS SDK in our crossbuild

[elasticmachine]

Pinging @elastic/agent (Team:Agent)

[kvch]

My test branch: #24251

[michel-laterman]

Updated crossbuild image to 1.16.4 elastic/golang-crossbuild#86

[michel-laterman]

@simitt, The golang-crossbuild images have been update to provide 1.16.4.
For MacOSX the golang-crossbuild:1.16.4-darwin-debian10 image provides the OSX 10.14 SDK (and artifacts will only run on 10.14+); the beats use this image to cross compile as there are issues building the beats when using go 1.16 with the earlier (10.11) SDK

[simitt]

Thanks for the ping @michel-laterman. So dropping support for OSX <10.14 is not considered a breaking change (it is done in a minor version upgrade)?
Referring to the current support matrix.

[michel-laterman]

@simitt, we are considering this a breaking change elastic/golang-crossbuild#87 (comment)
However MacOSX 10.13 went EOL December 2020, so the impact should be minimized.