Tools: Generate update images with managed bl mode

[theotherjimmy]

Description

This PR add generation of update images, which do not include the
bootloader, to managed bootloader mode builds. The output will include
Update Image: <image_name> to tell you where the update image is
located.

Resolves #7394

Pull request type

[ ] Fix
[ ] Refactor
[ ] New target
[x] Feature
[ ] Breaking change

[0xc0170]

@jorisa Please review

[cmonr]

/morph build

[mbed-ci]

Build : FAILURE

Build number : 2669
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7567/

[cmonr]

/morph build

[mbed-ci]

Build : ABORTED

Build number : 2671
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7567/

[cmonr]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 2672
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7567/

Triggering tests

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/morph mbed2-build

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Exporter Build : FAILURE

Build number : 2304
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7567/

[mbed-ci]

Test : SUCCESS

Build number : 2410
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7567/2410

[cmonr]

Silly export nodes...
/morph export-build

[mbed-ci]

Exporter Build : FAILURE

Build number : 2305
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7567/

[cmonr]

Hmmmmm......

/morph export-build

[mbed-ci]

Exporter Build : FAILURE

Build number : 2307
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7567/

[0xc0170]

/morph export-build

[mbed-ci]

Exporter Build : FAILURE

Build number : 2309
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7567/

[cmonr]

ಠ_ಠ

/morph export-build

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2311
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7567/