WIP: tls: make private-key and private-key-pem properties readable

This implements glib!2087, allowing applications to read the private-key
and private-key-pem properties, but only if the key is backed by memory
and not something like a PKCS #11 smartcard.
4 jobs for mcatanzaro/readable-private-key in 5 minutes and 37 seconds
Status Job ID Name Coverage
  Build
failed #1342431
fedora-x86_64

00:05:37

failed #1342432
asan
fedora-x86_64-asan

00:01:14

passed #1342433
fedora-x86_64-scan-build

00:00:35

failed #1342434
win32-ps
vs2017-x64

00:01:18

 
Name Stage Failure
failed
fedora-x86_64-asan Build
Skipped:            0   
Timeout: 0

Uploading artifacts for failed job
Uploading artifacts...
WARNING: _build/test-results: no matching files
ERROR: No files to upload
Cleaning up file based variables
ERROR: Job failed: exit code 1
failed
vs2017-x64 Build
GO version:   go1.13.8
Built: 2020-12-21T13:47:18+0000
OS/Arch: windows/amd64
Uploading artifacts...
Runtime platform
arch=amd64 os=windows pid=3832 revision=943fc252 version=13.7.0
WARNING: build/test-results: no matching files
ERROR: No files to upload
Cleaning up file based variables
ERROR: Job failed: exit status 1
failed
fedora-x86_64 Build
Timeout:            0   

Uploading artifacts for failed job
Uploading artifacts...
WARNING: _build/test-results: no matching files
ERROR: No files to upload
Cleaning up file based variables
ERROR: Failed to cleanup volumes
ERROR: Job failed: exit code 1