Feature: kots template

[nvanthao]

What this PR does / why we need it:

It is currently difficult to debug templating error thrown by KOTS during install.

Which issue(s) this PR fixes:

Special notes for your reviewer:

This PR introduce new command kots template with 4 options to parse template.

1. Parse raw template directly from --data flag.

E.g.

kots template --license-file license.yaml --config-values config.yaml --data '{{repl ConfigOption "hostname" | ToUpper }}'

MYHOST

2. Parse template interactively. New REPL session will be created to parse template

kots template --license-file license.yaml --config-values config.yaml --interactive

3. Parse template by file

kots template --license-file license.yaml --config-values config.yaml <path_to_template>

4. Parse all templates in kotsKind directory, this behave similar to helm template where all files in kotsKind directory will be printed to stdout. The app will be pulled from upstream.

kots template --license-file license.yaml --config-values config.yaml 

5. Parse all templates from local release.

kots template --license-file license.yaml --config-values config.yaml --local-path <path_to_release>

Does this PR introduce a user-facing change?

New command line command `kots template`

Does this PR require documentation?

Yes

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