Allow C pointers as valid self parameters in method detection

[fomgleb]

The language server was not recognizing methods with C pointer receivers ([*c]T) as valid methods on their container types. This meant that when working with C interop code, functions like fuse_opt_parse declared with [*c]struct_fuse_args parameters were not being offered as method completions on instances of struct_fuse_args.

Example of generated cimport.zig:

pub const struct_fuse_args = extern struct {
    argc: c_int = 0,
    argv: [*c][*c]u8 = null,
    allocated: c_int = 0,
    pub const fuse_opt_parse = __root.fuse_opt_parse;
    pub const parse = __root.fuse_opt_parse;
};
// Here, generated with `[*c]` pointer.
pub extern fn fuse_opt_parse(args: [*c]struct_fuse_args, data: ?*anyopaque, opts: [*c]const struct_fuse_opt, proc: fuse_opt_proc_t) c_int;

var fuse_args: c.struct_fuse_args = .{};

// This compiles, but no method completion was offered:
_ = fuse_args.parse(&options, &option_spec, null);

Solution

Updated firstParamIs to treat .c pointers the same as .one pointers when matching the container type.

[Techatrix]

Please send pull requests to the default branch (i.e. "master") instead of 0.16.x unless the change does not apply to master branch. Given that I deem this change eligible to be cherry picked into 0.16.x anyway, it's not a problem in this particular case.