[pkg/ottl] Split ConvertCase function to explicit functions for each case

[krokwen]

Component(s)

pkg/ottl

Is your feature request related to a problem? Please describe.

ConvertCase function accepts StringGetter first argument and could be used as converting function in functions like replace_all_patterns, but it requires the second argument, that makes impossible to use it in such case

Describe the solution you'd like

ToLowerCase("String") instead of ConvertCase("String", "lower")
ToUpperCase("String") instead of ConvertCase("String", "upper")
ToSnakeCase("String") instead of ConvertCase("String", "snake")
ToCamelCase("String") instead of ConvertCase("String", "camel")

Describe alternatives you've considered

No response

Additional context

Currently (using a bug, #32895 #32896) I use a SHA1 function with replace_all_patterns as fastest available option to convert the value under matching key, but i believe, case converting will be much faster, please correct me if i'm wrong

[github-actions]

Pinging code owners:

• pkg/ottl: @TylerHelmuth @kentquirk @bogdandrutu @evan-bradley

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[fede843]

Hi, ended up here looking for something like:

  `replace_all_patterns(attributes, "key", "http.request.header.(.+)", "$0", ConvertCase)`,

I actually would like to set those attributes all to lowercase. Since ConvertCase has an extra arg I cannot do it.
I have also noticed, for sake of testing, that even with SHA1 as function, that changed the value. I would have expected the key to be replaced. Related to #32895 #32896 mentioned above

[github-actions]

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Pinging code owners:

• pkg/ottl: @TylerHelmuth @kentquirk @bogdandrutu @evan-bradley

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