Add support for Vim9 script code coverage

[yegappan]

I am trying to use covimerage to collect the code coverage information for the Vim9 LSP plugin.
Currently the script fails: https://github.com/yegappan/lsp/runs/4907890136?check_suite_focus=true.
Can covimerage be enhanced to support Vim9 scripts?

[blueyed]

I haven't tested it myself, but apparently it needs adjustments, and/or shows incompatibilities with Vim's profiling output that is used.

Some output from your CI job:

Script line does not match function line, ignoring: '  return lnums->sort((a, b) => a - b)' != 'return v->str2nr()'.
Script line does not match function line, ignoring: 'enddef' != 'return a - b'.
Script line does not match function line, ignoring: '      autocmd CursorMoved <buffer> call lsp#docHighlightClear()' != '      autocmd CursorMoved <buffer> call lsp#docHighlightClear() | call lsp#docHighlight()'.
Script line does not match function line, ignoring: '  return lnums->sort((a, b) => a - b)' != 'return v->str2nr()'.
Script line does not match function line, ignoring: 'enddef' != 'return a - b'.
Script line does not match function line, ignoring: '      autocmd CursorMoved <buffer> call lsp#docHighlightClear()' != '      autocmd CursorMoved <buffer> call lsp#docHighlightClear() | call lsp#docHighlight()'.
Script line does not match function line, ignoring: 'enddef' != 'return a - b'.
Script line does not match function line, ignoring: '  return lnums->sort((a, b) => a - b)' != 'return v->str2nr()'.
Script line does not match function line, ignoring: 'enddef' != 'return a - b'.
Script line does not match function line, ignoring: '  return lnums->sort((a, b) => a - b)' != 'return v->str2nr()'.
Script line does not match function line, ignoring: 'enddef' != 'return a - b'.
Script line does not match function line, ignoring: '      autocmd CursorMoved <buffer> call lsp#docHighlightClear()' != '      autocmd CursorMoved <buffer> call lsp#docHighlightClear() | call lsp#docHighlight()'.
Script line does not match function line, ignoring: 'enddef' != 'return a - b'.
Script line does not match function line, ignoring: '      autocmd CursorMoved <buffer> call lsp#docHighlightClear()' != '      autocmd CursorMoved <buffer> call lsp#docHighlightClear() | call lsp#docHighlight()'.
Script line does not match function line, ignoring: '  return lnums->sort((a, b) => a - b)' != 'return v->str2nr()'.
Script line does not match function line, ignoring: 'enddef' != 'return a - b'.
Script line does not match function line, ignoring: '      autocmd CursorMoved <buffer> call lsp#docHighlightClear()' != '      autocmd CursorMoved <buffer> call lsp#docHighlightClear() | call lsp#docHighlight()'.
Script line does not match function line, ignoring: '  return lnums->sort((a, b) => a - b)' != 'return v->str2nr()'.
Script line does not match function line, ignoring: 'enddef' != 'return a - b'.
Could not find source for function: <SNR>14_processInitializeReply
Could not find source for function: <lambda>1
Could not find source for function: <lambda>2
Writing coverage file .coverage_covimerage.