Add GetOutputMetadata to the output reader

[pingsutw]

TL;DR

Add GetOutputMetadata to the output reader, so the propeller can retrieve the deck path by calling this method.

Type

• Bug Fix
• Feature
• Plugin

Are all requirements met?

• Code completed
• Smoke tested
• Unit tests added
• Code documentation added
• Any pending items have an associated Issue

Complete description

^^^

Tracking Issue

flyteorg/flyte#2603

Follow-up issue

flyteorg/flytepropeller#494

[codecov]

Codecov Report

Merging #289 (4fa6067) into master (eed7326) will increase coverage by 0.00%.
The diff coverage is 66.66%.

@@ Coverage Diff @@## master #289 +/- ##
=======================================
Coverage 63.32% 63.32% =======================================
Files 145 145 Lines 9311 9317 +6 =======================================
+ Hits 5896 5900 +4 - Misses 2872 2873 +1 - Partials 543 544 +1 

Flag	Coverage Δ
unittests	62.73% <50.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...ks/pluginmachinery/core/allocationstatus_enumer.go	0.00% <ø> (ø)
go/tasks/pluginmachinery/core/phase_enumer.go	13.33% <ø> (ø)
...asks/pluginmachinery/core/transitiontype_enumer.go	13.33% <ø> (ø)
...inery/flytek8s/resourcecustomizationmode_enumer.go	13.33% <ø> (ø)
...ks/pluginmachinery/internal/webapi/phase_enumer.go	13.33% <ø> (ø)
go/tasks/pluginmachinery/ioutils/paths.go	84.61% <ø> (ø)
...sks/pluginmachinery/workqueue/workstatus_enumer.go	13.33% <ø> (ø)
go/tasks/plugins/array/core/phase_enumer.go	13.33% <ø> (ø)
...pluginmachinery/ioutils/in_memory_output_reader.go	65.21% <50.00%> (-3.21%)	⬇️
...uginmachinery/ioutils/remote_file_output_reader.go	22.07% <100.00%> (+2.07%)	⬆️

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