Add RemoteInput.open

[tikkss]

GitHub: GH-5

This patch will introduce the new high level API for IO like object (input only object, read only object).

RemoteInput.open downloads the data lazily on the first read. The data is stored in a system cache directory and kept on close to avoid re-download for the same URL:

RemoteInput.open("https://example.com/sample/data.csv") do |input|
  input.read
end

The cache file path is computed from the URL so that the same URL uses the same cache:

• URL: https://example.com/sample/data.csv
• Cache file path: <system cache directory>/red-remote-input/example.com-sample/data.csv
  • example.com-sample is the cache ID: host + directory (/ is replaced with -)
  • data.csv is the base name of the URL
    (data is used when the URL doesn't have a base name)

RemoteInput#clear_cache removes the cache explicitly:

input = RemoteInput.open("https://example.com/sample/data.csv")
input.read
input.close       # The cache is kept here
input.clear_cache # Remove the cache explicitly

RemoteInput.open accepts encoding options like IO.new:

RemoteInput.open("https://example.com/sample/data.csv",
                 encoding: "Windows-31J:UTF-8") do |input|
  input.read # => UTF-8 string
end

Without a block, RemoteInput.open returns a RemoteInput object that must be closed explicitly:

input = RemoteInput.open("https://example.com/sample/data.csv")
input.read
input.close

[tikkss]

GitHub Actions was disabled when I opened this PR, so no workflows ran.
I've since enabled it, but since events aren't re-delivered, I'll close and reopen this PR to trigger CI.

[tikkss]

I've made RemoteInput a class and moved the RemoteInput::Input implementation to it: c547b94
I've also merged test/test-input.rb into test/test-remote-input.rb.
Could you review this again? Thanks!

[tikkss]

I've applied the suggestions:

• Removed mode and added encoding:/internal_encoding:/external_encoding:
  options like IO.new
• Used the same cache ID for the same URL: the cache ID is computed from
  the URL (host + directory, / is replaced with -), e.g.
  https://example.com/sample/data.csv → example.com-sample/data.csv
• Kept the cache file on close to avoid re-download and added
  RemoteInput#clear_cache to remove it explicitly

I've also updated the PR title and description for the new design.
Could you review this again?

[tikkss]

I've applied all suggestions and updated the PR description. Could you review this again?

Note: making #path a public API (that downloads the data lazily) is out of scope of this PR.

[tikkss]

Thanks for your polite review always!