pwndbg "Move GDB initialization and basic startup functionality to a new Debugger-agnostic API"

[Acters]

pwndbg/pwndbg@7dbc547

the 3 month old commit breaks provided script of pwngdb to pwndbg.

consider changing it from $pwndbg/pwndbg/__init__.py to $pwndbg/pwndbg/dbg/gdb.py
and change import pwndbg.commands.pwngdb and import pwndbg.commands.angelheap to:
from pwndbg.commands import pwngdb and from pwndbg.commands import angelheap

this should be new README.md now:

# Pwngdb ❤️ pwndbg

Below instruction is tested based on Pwndbg: `2024.02.14 build: 90dc42e5`.

## How to install

1. Put `pwngdb.py` and `angelheap.py` into `/path/to/pwndbg/pwndbg/`

2. Put `commands/pwngdb.py` and `commands/angelheap.py` into `/path/to/pwndbg/pwndbg/commands/`

3. Add  `from pwndbg.commands import pwngdb` and `from pwndbg.commands import angelheap` into `/path/to/pwndbg/pwndbg/dbg/gdb.py`

You can use these commands to install it:

```shell
#!/bin/bash
# You need to change the `/path/to/pwdbg` to your pwndbg location

pwndbg='/path/to/pwndbg'

cp pwngdb.py $pwndbg/pwndbg/pwngdb.py
cp angelheap.py $pwndbg/pwndbg/angelheap.py

cp commands/pwngdb.py $pwndbg/pwndbg/commands/pwngdb.py
cp commands/angelheap.py $pwndbg/pwndbg/commands/angelheap.py

sed -i -e '/def setup(self):/a \        from pwndbg.commands import pwngdb' $pwndbg/pwndbg/dbg/gdb.py
sed -i -e '/def setup(self):/a \        from pwndbg.commands import angelheap' $pwndbg/pwndbg/dbg/gdb.py
```.

## Note

To avoid the conflict with pwndbg, some commands will be different or be removed.

1. `got` will be renamed to `objdump_got`

2. `canary` will be removed since pwndbg already has `canary` command

3. `tls` will be renamed to `pwngdb_tls`

## TODO

- [ ] Use more pwndbg API if possible instead of using `gdb.execute` (see [developer notes of pwndbg](https://github.com/pwndbg/pwndbg/blob/dev/DEVELOPING.md))