fix: Go default template doesn't work for tagging

[ericzzzzzzz]

Fixes: #8872

Description

• This pr changes how we handle missing key when evaluating Go template for generating tags
• The original one errors out too early before we can use other Go template method to handle missing key with customization
• Changing this option to missingkey=invalid allow us to use other Go template method to handle missing key, for example default go template method , the evaluation for '{{default "bar" .FOO}}' should be "bar" when using envTemplateTagger when .FOO is missing
• The original business logic won't change -- fallback to latest tagger if missing keys were not handled with other go templates method, as missingkey=invalid strategy will put <no value> in templating result if the key not handled by other methods, we return error by checking if output contains <no value>, so this behave the same as the current one.