* Updates `ale#lsp#response#ReadDiagnostics` to always store the full, unaltered diagnostic message from the LSP in question. The current process is to replace all newline characters with whitespace (' '), which then leads to broken formatting when viewing complex output from an LSP with `:ALEDetail` and other commands.
* Updates `ale#cursor#TruncatedEcho` to replace newline characters with a space ' ' instead of an empty string '' to retain the previous style of formatting for echoed messages.
Fixes: #2356Fixes: #3068Fixes: #2301
Implement pull diagnostics in the VimL implementation so ALE is able
to track when servers are busy checking files. Only servers that
support this feature will return diagnostics these ways.
