Handle conflicts when 2 modes are activated simultaneously

[csd1100]

Suppose there are two modes A, B and they are activated one after other.
Then behavior should be of last-in-wins. i.e. keymaps of B will be used.
For conflicts following should be the behavior:

Step 1: When mode A is activated:

1. Any existing global keymaps that conflict should be backed up
2. Keymaps defined for A should be applied

Step 2. When mode B is activated:

1. Any existing global keymaps that conflict with B should be backed up
2. Any keymaps for A that conflict with B should be backed up
3. Keymaps defined for B should be applied

Step 3: Mode deactivation scenarios

If A is deactivated first:

1. All maps of A that do not conflict with B should removed.
2. Maps of B should not be touched.
3. Keys backed up by B for A should be replaced with keys backed up by A.
4. When B deactivates Backup created by B should be applied along with replaced
   maps in above step.

If B is deactivated first:

1. All maps of B should be removed.
2. Backup of existing keys including backed up maps of A should be applied.