fix(eval/method): add missing method support for existing built-ins

These functions were ported with the vim-patch token, but didn't actually port
the method call support that was in their patches (method call syntax wasn't
ported yet).

Add the missing method call support and latest docs for:
 - assert_nobeep:
   5b8cabfef7
 - buffer_name, buffer_number: (obsolete)
   a8eee21e75
 - charidx:
   17793ef23a
 - flatten:
   077a1e670a
 - prompt_getprompt:
   077cc7aa0e
 - searchcount:
   e8f5ec0d30
 - strptime:
   10455d43fe
 - win_gettype:
   00f3b4e007
 - win_splitmove:
   d20dcb3d01

Also fix assert_beeps, assert_nobeep and getenv to accept exactly one argument.
Previously, they could erroneously accept one or more.

src/nvim/eval.lua

@@ -33,7 +33,7 @@ return {
     arglistid={args={0, 2}},
     argv={args={0, 2}},
     asin={args=1, base=1, func="float_op_wrapper", data="&asin"},  -- WJMc
-    assert_beeps={args={1}, base=1},
+    assert_beeps={args=1, base=1},
     assert_equal={args={2, 3}, base=2},
     assert_equalfile={args={2, 3}, base=1},
     assert_exception={args={1, 2}},
@@ -41,7 +41,7 @@ return {
     assert_false={args={1, 2}, base=1},
     assert_inrange={args={3, 4}, base=3},
     assert_match={args={2, 3}, base=2},
-    assert_nobeep={args={1}},
+    assert_nobeep={args=1, base=1},
     assert_notequal={args={2, 3}, base=2},
     assert_notmatch={args={2, 3}, base=2},
     assert_report={args=1, base=1},
@@ -53,8 +53,8 @@ return {
     bufadd={args=1, base=1},
     bufexists={args=1, base=1},
     buffer_exists={args=1, base=1, func='f_bufexists'},  -- obsolete
-    buffer_name={args={0, 1}, func='f_bufname'},  -- obsolete
-    buffer_number={args={0, 1}, func='f_bufnr'},  -- obsolete
+    buffer_name={args={0, 1}, base=1, func='f_bufname'},  -- obsolete
+    buffer_number={args={0, 1}, base=1, func='f_bufnr'},  -- obsolete
     buflisted={args=1, base=1},
     bufload={args=1, base=1},
     bufloaded={args=1, base=1},
@@ -71,7 +71,7 @@ return {
     chanclose={args={1, 2}},
     chansend={args=2},
     char2nr={args={1, 2}, base=1},
-    charidx={args={2, 3}},
+    charidx={args={2, 3}, base=1},
     chdir={args=1, base=1},
     cindent={args=1, base=1},
     clearmatches={args={0, 1}, base=1},
@@ -121,7 +121,7 @@ return {
     filter={args=2, base=1},
     finddir={args={1, 3}, base=1},
     findfile={args={1, 3}, base=1},
-    flatten={args={1, 2}},
+    flatten={args={1, 2}, base=1},
     float2nr={args=1, base=1},
     floor={args=1, base=1, func="float_op_wrapper", data="&floor"},
     fmod={args=2, base=1},
@@ -152,7 +152,7 @@ return {
     getcompletion={args={2, 3}, base=1},
     getcurpos={},
     getcwd={args={0, 2}, base=1},
-    getenv={args={1}, base=1},
+    getenv={args=1, base=1},
     getfontname={args={0, 1}},
     getfperm={args=1, base=1},
     getfsize={args=1, base=1},
@@ -262,7 +262,7 @@ return {
     pow={args=2, base=1},
     prevnonblank={args=1, base=1},
     printf={args=varargs(1), base=2},
-    prompt_getprompt={args=1},
+    prompt_getprompt={args=1, base=1},
     prompt_setcallback={args={2, 2}, base=1},
     prompt_setinterrupt={args={2, 2}, base=1},
     prompt_setprompt={args={2, 2}, base=1},
@@ -299,7 +299,7 @@ return {
     screenrow={},
     screenstring={args=2, base=1},
     search={args={1, 4}, base=1},
-    searchcount={args={0,1}},
+    searchcount={args={0, 1}, base=1},
     searchdecl={args={1, 3}, base=1},
     searchpair={args={3, 7}},
     searchpairpos={args={3, 7}},
@@ -359,7 +359,7 @@ return {
     string={args=1, base=1},
     strlen={args=1, base=1},
     strpart={args={2, 4}, base=1},
-    strptime={args=2},
+    strptime={args=2, base=1},
     strridx={args={2, 3}, base=1},
     strtrans={args=1, base=1},
     strwidth={args=1, base=1},
@@ -407,12 +407,12 @@ return {
     win_execute={args={2, 3}, base=2},
     win_findbuf={args=1, base=1},
     win_getid={args={0, 2}, base=1},
-    win_gettype={args={0,1}},
+    win_gettype={args={0, 1}, base=1},
     win_gotoid={args=1, base=1},
     win_id2tabwin={args=1, base=1},
     win_id2win={args=1, base=1},
     win_screenpos={args=1, base=1},
-    win_splitmove={args={2, 3}},
+    win_splitmove={args={2, 3}, base=1},
     winbufnr={args=1, base=1},
     wincol={},
     windowsversion={},