editors/neovim: Update to 0.5.1

BREAKING CHANGES:
feat(lua)!: register_keystroke_callback => on_key
feat(lsp)!: change handler signature #15504

FEATURES:
feat(jobstart): add parameter to close stdin

FIXES:
backport: fix(windowing): positioning of relative floats
backport: refactor(sign): include longer sign column option
backport: fix(sign): reset auto sign column with minimum in float win minimal style
backport: fix(decorations): crash when :bdelete (extmark_free_all) after clear_namespace
build: use RelWithDebInfo build for nightlies, Release for releases
build: update appdata.xml version in release commit
test(treesitter): skip all parsers tests if parsers aren't installed
Rename stdin to stdin_mode (fixes Windows build)

FIXES (LSP):
backport: fix(lsp): Ensure human readable errors are printed
backport: fix(lsp): Ensure users get feedback on references/symbols errors or empty results
backport: fix(lsp): prevent double <text> for cached plaintext markup
feat(lsp): allow root_dir to be nil (#15430) (Mathias Fußenegger)
lsp(start_client): Allow passing custom workspaceFolders to the LSP (#15132) (sim)
fix(lsp): check if buffer is valid in changetracking (#15505) (Jose Alvarez)
fix(lsp): avoid ipairs on non-sequential tables (#15059) (Michael Lingelbach)
feat(lsp): improve vim.lsp.util.apply_text_edits (#15561) (hrsh7th)
feat(lsp): improve logging (#15636) (Michael Lingelbach)