Add RPC docs for older Bitcoin Core versions

[0xB10C]

As mentioned by @fanquake in https://github.com/bitcoin-core/bitcoincore.org/pull/914#issuecomment-1313940393, we might want to add RPC docs for some older Bitcoin Core versions. Comparing bitcoin/bitcoin tags with the docs available (< means missing):

0.8.0         <
0.8.1         <
0.8.2         <
0.8.3         <
0.8.4         <
0.8.5         <
0.8.6         <
0.9.0         <
0.9.1         <
0.9.2         <
0.9.2.1       <
0.9.3         <
0.9.4         <
0.9.5         <
0.10.0        <
0.10.1        <
0.10.2        <
0.10.3        <
0.10.4        <
0.10.5        <
0.11.0        <
0.11.1        <
0.11.2        <
0.11.3        <
0.12.0        <
0.12.1        <
0.13.0        <
0.13.1        <
0.13.2        <
0.14.0        <
0.14.1        <
0.14.2        <
0.14.3        <
0.15.0        <
0.15.0.1      <
0.15.1        <
0.15.2        <
0.16.0      0.16.0
0.16.1      0.16.1
0.16.2      0.16.2
0.16.3      0.16.3
0.17.0      0.17.0
0.17.0.1      <
0.17.1        <
0.17.2        <
0.18.0      0.18.0
0.18.1        <
0.19.0      0.19.0
0.19.0.1      <
0.19.1        <
0.19.2        <
0.20.0      0.20.0
0.20.1        <
0.20.2        <
0.21.0      0.21.0
0.21.1        <
0.21.2        <
22.0.0      22.0.0
23.0.0          23.0.0

To discuss:

• Should we add old docs? Do they provide value?
• How far back should we add RPC docs?
• Only major releases?

[0xB10C]

I'd be happy to pick up adding a few of these if there's agreement that this is something we think is valuable.

[0xB10C]

For reference, there's also https://github.com/bitcoin-core/bitcoincore.org/issues/590

[katesalazar]

duplicate of #590, can close