Allow Auth with Username and Password for TelemetryService MQTT

[rhoninl]

What this PR does / why we need it:
Some MQTT Endpoint need to config username or password to conenct it
Will this PR make the community happier?

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #

How is this PR tested

• unit test
• e2e test
• other (please specify)

Special notes for your reviewer:

Release note:

- update telemetryService MQTT Secret inject Logic
- Add MQTTServerUserName to allow user to Auth with UserName and Password
- Update CRD add MQTTServerUserName to allow user to input Username using plaintext

[tomqin93]

Please include document changes as well

[rhoninl]

Please include document changes as well

Edgenesis/shifu.dev#297

[tomqin93]

@rhoninl added some comment, please take a look

[tomqin93]

@rhoninl added 1 minor comment, need to add tests for username+password for telemetryservicemqtt

[tomqin93]

LGTM