cleanup: add IPsec ESP transport support, packet print debug functions, and misc cleanup.

[philljj]

Description

• Add IPsec ESP transport mode support.
• Fix gcc15 build error (error: initializer-string for array).
• Update gitignore.
• Add convenience debug packet print functions for: eth, ip, tcp, esp.
• misc cleanup.

Testing

Set ip xfrm state / policy with script:

./scripts/ip-xfrm/cbc_auth sha256 128 

DEBUG_IP + DEBUG_ESP output from ./build/test-evloop

ip hdr:
+-----------------------------+
| 0x04 | 0x45 | 0x00 |    108 | (ipv, hdr_len, tos, ip_len)
+-----------------------------+
|    0xc625    |    0x4000    | (id, flags_fo)
+-----------------------------+
|   64  | 0x32 |    0x4c24    | (ttl, proto, chksum)
+-----------------------------+
|                10.10.10.1   | (src)
+-----------------------------+
|                10.10.10.2   | (dst)
+-----------------------------+

info: found sa: 0x764f47c9
info: aes cbc dec
esp packet: (88 bytes)
+------------------+
|  76  4f  47  c9  | (spi, 4 bytes)
+------------------+
|  00  00  00  02  | (seq, 4 bytes)
+------------------+
|  1e  ae  19  4d  | (iv, 16 bytes)
|  9c  c9  86  95  |
|  82  e2  bc  c7  |
|  f7  0f  17  d7  |
+------------------+
|  b7  98  00  08  | (payload, 56 bytes)
|  bd  45  e2  28  |
|  00  00  00  00  |
|  a0  02  fa  f0  |
|  76  73  00  00  |
|  ..  ..  ..  ..  |
+------------------+
| 0506 | 06 | 0x06 | (padding last 2 bytes, pad len, nxt hdr)
+------------------+
|  5e  eb  f7  c9  | (icv, 16 bytes)
|  b0  a9  7d  78  |
|  e8  b2  06  20  |
|  32  ea  82  9e  |
+------------------+