Implement motions: [m and ]m (go to method)

Is your feature request related to a problem? Please describe.
When working with Java files where everything is inside a class, it's very useful to navigate to the start or end of methods. Currently, there is no easy way to do this in VSCodeVim since the Vim method navigation motions (mainly [m and ]m) are missing. So I'm left with relative line jumping or guessing [{ to achieve the same result that a single [m/]m would do.

Describe the solution you'd like
In Vim, method navigation is done with the key maps ]m (next method start) and [m (previous method start). Similarly, ]M (next method end) and [M (previous method end) also exist to go to the end of methods.

Please implement these key maps (]m/[m/]M/[M), following the behavior of Vim (https://vimhelp.org/motion.txt.html#%5Dm). In my opinion, the most useful mappings are ]m and [m, so I think that at least those should be implemented (hence the title of the issue).

Describe alternatives you've considered

• Use this plugin to navigate only method members: https://github.com/mishkinf/vscode-goto-next-previous-member
  • Problems:
    • The cursor does not go to the starting brace of the methods, it goes to the method name (not Vim's behavior).
    • Not sure if possible to implement ]M and [M using this plugin.
• Don't try to use ]m/[m/etc. altogether and instead rely on other Vim motions.
  • Relative line jump
    • Problems:
      • The command is not always the same (the count may be different).
      • Not viable when the method is too long that the method signature is not visible in the editor.
  • Motions [{/]}
    • Problems:
      • The command may have to be typed more than once (since a single execution may not be enough, like when the cursor is inside an if statement).

Additional context
Vim help on these method motions: https://vimhelp.org/motion.txt.html#%5Dm

Demo of the desired behavior. Going up the file with [m and down with ]M:

Start with the Vim motion.txt documentation linked in the issue and review how the VSCodeVim extension currently handles motion key maps. Define behavior for ]m, [m, ]M, and [M across supported Java and other language files, including counts and method boundaries. Done means the mappings match Vim's documented navigation behavior and are covered by appropriate extension tests.