feat(eval/method): partially port v8.1.1953

Adds method call support for all functions in the patch, but it cannot
be fully ported due to missing tests for:

- index(): requires Blobs from v8.1.0735.
           Note that index() was already added as a method in v8.1.1803;
           this patch only adds a test.

- iconv(): requires v8.1.1136 for test_termcodes.vim.

Nvim deprecated inputdialog(), so it no longer has an eval.txt entry.

Keep the test for hlexists() commented-out, just like previously. (Nvim
always defines the Number group, so it always returns 1 instead)

Cannot include both changes to test_syn_attr.vim as Nvim doesn't support
":hi term=..."; however, both test the same ->hlID() syntax anyway.

src/nvim/eval.lua

@@ -183,32 +183,32 @@ return {
     globpath={args={2, 5}, base=2},
     has={args=1},
     has_key={args=2, base=1},
-    haslocaldir={args={0,2}},
-    hasmapto={args={1, 3}},
-    highlightID={args=1, func='f_hlID'},  -- obsolete
-    highlight_exists={args=1, func='f_hlexists'},  -- obsolete
-    histadd={args=2},
-    histdel={args={1, 2}},
-    histget={args={1, 2}},
-    histnr={args=1},
-    hlID={args=1},
-    hlexists={args=1},
+    haslocaldir={args={0, 2}, base=1},
+    hasmapto={args={1, 3}, base=1},
+    highlightID={args=1, base=1, func='f_hlID'},  -- obsolete
+    highlight_exists={args=1, base=1, func='f_hlexists'},  -- obsolete
+    histadd={args=2, base=2},
+    histdel={args={1, 2}, base=1},
+    histget={args={1, 2}, base=1},
+    histnr={args=1, base=1},
+    hlID={args=1, base=1},
+    hlexists={args=1, base=1},
     hostname={},
-    iconv={args=3},
-    indent={args=1},
+    iconv={args=3, base=1},
+    indent={args=1, base=1},
     index={args={2, 4}, base=1},
-    input={args={1, 3}},
-    inputdialog={args={1, 3}},
-    inputlist={args=1},
+    input={args={1, 3}, base=1},
+    inputdialog={args={1, 3}, base=1},
+    inputlist={args=1, base=1},
     inputrestore={},
     inputsave={},
-    inputsecret={args={1, 2}},
+    inputsecret={args={1, 2}, base=1},
     insert={args={2, 3}, base=1},
     interrupt={args=0},
     invert={args=1, base=1},
-    isdirectory={args=1},
+    isdirectory={args=1, base=1},
     isinf={args=1, base=1},
-    islocked={args=1},
+    islocked={args=1, base=1},
     isnan={args=1, base=1},
     id={args=1},
     items={args=1, base=1},