chore: build pg15 with docker

[sweatybridge]

What kind of change does this PR introduce?

feature

What is the new behavior?

• Build Postgres from source with official PPA flags and graviton optimisations
• Improved performance in all 3 benchmarks over generic build.

AMI Build	TPCB-like	select-only	simple-update	Flags
15.1.0.75	150.575 ms	6.591 ms	17.112 ms	-mcpu=native
15.1.0.86-rc1	112.694 ms	6.608 ms	17.834 ms	Official PPA
15.1.0.89-rc1	109.967 ms	6.126 ms	16.505 ms	PPA + mcpu

All benchmarks are run on m6g.xlarge instances on staging, using pgbench with postgres 15.1.

Additional context

tpcb-like: 109.967 ms

postgres@db-agbqdybysfheblwajkpx:/home/ubuntu$ pgbench -c 100 -T 60 -b tpcb-like
pgbench (15.1 (Ubuntu 15.1-1.pgdg20.04+1))
starting vacuum...end.
transaction type: <builtin: TPC-B (sort of)>
scaling factor: 1
query mode: simple
number of clients: 100
number of threads: 1
maximum number of tries: 1
duration: 60 s
number of transactions actually processed: 54191
number of failed transactions: 0 (0.000%)
latency average = 109.967 ms
initial connection time = 610.771 ms
tps = 909.365320 (without initial connection time)

simple select: 6.126 ms

postgres@db-agbqdybysfheblwajkpx:/home/ubuntu$ pgbench -c 100 -T 60 -b select-only
pgbench (15.1 (Ubuntu 15.1-1.pgdg20.04+1))
starting vacuum...end.
transaction type: <builtin: select only>
scaling factor: 1
query mode: simple
number of clients: 100
number of threads: 1
maximum number of tries: 1
duration: 60 s
number of transactions actually processed: 971096
number of failed transactions: 0 (0.000%)
latency average = 6.126 ms
initial connection time = 604.199 ms
tps = 16323.771087 (without initial connection time)

simple update: 16.505 ms

postgres@db-agbqdybysfheblwajkpx:/home/ubuntu$ pgbench -c 100 -T 60 -b simple-update
pgbench (15.1 (Ubuntu 15.1-1.pgdg20.04+1))
starting vacuum...end.
transaction type: <builtin: simple update>
scaling factor: 1
query mode: simple
number of clients: 100
number of threads: 1
maximum number of tries: 1
duration: 60 s
number of transactions actually processed: 360550
number of failed transactions: 0 (0.000%)
latency average = 16.505 ms
initial connection time = 606.376 ms
tps = 6058.872750 (without initial connection time)