Eglot: add support for insertReplaceEdit (bug#73857)

Eglot: add support for insertReplaceEdit (bug#73857)

* lisp/progmodes/eglot.el (eglot-server-programs): Mention zig-ts-mode.
(eglot--lsp-interface-alist): Describe 'InsertReplaceEdit'.
(eglot-client-capabilities): Advertise 'insertReplaceSupport'.
(eglot-completion-at-point): Consider 'InsertReplaceEdit'.
(eglot--apply-text-edits): Consider 'InsertReplaceEdit'.

* test/lisp/progmodes/eglot-tests.el
(eglot-test-zig-insert-replace-completion): New test.

Special thanks to kcbanner@gmail.com

(cherry picked from commit 1143cf09a339d57051a4341103c9e342d8876649)