Rename functions. eglot--request is now the synchronous one

Rename functions. eglot--request is now the synchronous one

* eglot.el (eglot--connect, eglot-shutdown)
(xref-backend-identifier-completion-table)
(xref-backend-definitions, xref-backend-references)
(xref-backend-apropos, eglot-completion-at-point, eglot-rename):
Call eglot--request.
(eglot--async-request): Renamed from eglot--request.
(eglot--request): Renamed from eglot--sync-request.
(eglot--TextDocumentIdentifier)
(eglot--VersionedTextDocumentIdentifier)
(eglot--TextDocumentPositionParams, eglot--TextDocumentItem):
Renamed from the more verbose eglot--current-buffer-* variante.
(eglot-rename, eglot-imenu, eglot-eldoc-function)
(eglot-completion-at-point, xref-backend-definitions)
(xref-backend-identifier-at-point)
(eglot--signal-textDocument/didSave)
(xref-backend-identifier-completion-table)
(eglot--signal-textDocument/didClose)
(eglot--signal-textDocument/didOpen)
(eglot--signal-textDocument/didChange): Use new function names.