tmux indicates its RGB support via setrgbb and setrgbf. In modern tmux
code, Tc and RGB just set setrgbb and setrgbf, so we can just check for
them.

Link: https://github.com/tmux/tmux/commit/7eb496c00c313c2f8ab8debe6d154d5ac0db277b

Problem:
`:checkhealth nvim` warns about missing vimrc if `init.lua` exists but
`init.vim` does not.

Solution:
Check for any of: init.vim, init.lua, $MYVIMRC.
Fix #25291

The following functions are deprecated and will be removed in
Nvim v0.11:

- health#report_start()
- health#report_info()
- health#report_ok()
- health#report_warn()
- health#report_error()
- vim.health.report_start()
- vim.health.report_info()
- vim.health.report_ok()
- vim.health.report_warn()
- vim.health.report_error()

Users should instead use these:

- vim.health.start()
- vim.health.info()
- vim.health.ok()
- vim.health.warn()
- vim.health.error()

* feat(lua): vim.tbl_contains supports general tables and predicates

Problem: `vim.tbl_contains` only works for list-like tables (integer
keys without gaps) and primitive values (in particular, not for nested
tables).

Solution: Rename `vim.tbl_contains` to `vim.list_contains` and add new
`vim.tbl_contains` that works for general tables and optionally allows
`value` to be a predicate function that is checked for every key.

In a few places ipairs was used to iterate over elements of the array.
However, the first return value of ipairs was erronously used, which is
not the value, but rather the index. This would result in errors, for
instance when trying to retrieve a field from the value.

This value can not be relied on as it doesn't work for
multi-configuration generators. I don't think this undocumented option
is used much, if at all, so I think we should remove it.