feat(lua): show proper verbose output for lua configuration

`:verbose` didn't work properly with lua configs (For example:
    options or keymaps are set from lua, just say that they were set
    from lua, doesn't say where they were set at.

This fixes that issue. Now `:verbose` will provide filename and line no
when option/keymap is set from lua.

Changes:
  - compiles lua/vim/keymap.lua as vim/keymap.lua
 - When souring a lua file current_sctx.sc_sid is set to SID_LUA
 - Moved finding scripts SID out of `do_source()` to `get_current_script_id()`.
   So it can be reused for lua files.
 - Added new function `nlua_get_sctx` that extracts current lua scripts
   name and line no with debug library. And creates a sctx for it.
     NOTE: This function ignores C functions and blacklist which
     currently contains only vim/_meta.lua so vim.o/opt wrappers aren't
     targeted.
 - Added function `nlua_set_sctx` that changes provided sctx to current
   lua scripts sctx if a lua file is being executed.
 - Added tests in tests/functional/lua/verbose_spec.lua
 - add primary support for additional types (:autocmd, :function, :syntax) to lua verbose
    Note: These can't yet be directly set from lua but once that's possible
    :verbose should work for them hopefully :D
 - add :verbose support for nvim_exec & nvim_command within lua
    Currently auto commands/commands/functions ... can only be defined
    by nvim_exec/nvim_command this adds support for them. Means if those
    Are defined within lua with vim.cmd/nvim_exec :verbose will show their
    location . Though note it'll show the line no on which nvim_exec call was made.

test/functional/api/keymap_spec.lua

@@ -15,6 +15,9 @@ local pcall_err = helpers.pcall_err
 local shallowcopy = helpers.shallowcopy
 local sleep = helpers.sleep
 
+local sid_api_client = -9
+local sid_lua = -8
+
 describe('nvim_get_keymap', function()
   before_each(clear)
 
@@ -340,7 +343,7 @@ describe('nvim_get_keymap', function()
       script=0,
       silent=0,
       expr=0,
-      sid=0,
+      sid=sid_lua,
       buffer=0,
       nowait=0,
       mode='n',
@@ -357,7 +360,7 @@ describe('nvim_get_keymap', function()
       script=0,
       silent=0,
       expr=0,
-      sid=0,
+      sid=sid_api_client,
       buffer=0,
       nowait=0,
       mode='n',
@@ -400,7 +403,7 @@ describe('nvim_set_keymap, nvim_del_keymap', function()
     to_return.silent = not opts.silent and 0 or 1
     to_return.nowait = not opts.nowait and 0 or 1
     to_return.expr = not opts.expr and 0 or 1
-    to_return.sid = not opts.sid and 0 or opts.sid
+    to_return.sid = not opts.sid and sid_api_client or opts.sid
     to_return.buffer = not opts.buffer and 0 or opts.buffer
     to_return.lnum = not opts.lnum and 0 or opts.lnum
     to_return.desc = opts.desc
@@ -625,7 +628,7 @@ describe('nvim_set_keymap, nvim_del_keymap', function()
   it('interprets control sequences in expr-quotes correctly when called '
      ..'inside vim', function()
     command([[call nvim_set_keymap('i', "\<space>", "\<tab>", {})]])
-    eq(generate_mapargs('i', '<Space>', '\t', {}),
+    eq(generate_mapargs('i', '<Space>', '\t', {sid=0}),
        get_mapargs('i', '<Space>'))
     feed('i ')
     eq({'\t'}, curbufmeths.get_lines(0, -1, 0))
@@ -807,7 +810,7 @@ describe('nvim_set_keymap, nvim_del_keymap', function()
     local mapargs = funcs.maparg('asdf', 'n', false, true)
     assert.Truthy(type(mapargs.callback) == 'number', 'callback is not luaref number')
     mapargs.callback = nil
-    eq(generate_mapargs('n', 'asdf', nil, {}), mapargs)
+    eq(generate_mapargs('n', 'asdf', nil, {sid=sid_lua}), mapargs)
   end)
 
   it('can make lua expr mappings', function()