wallet: more accurate blockchain height approximation

[SNeedlewoods]

Issue short description

restore_height can be set higher than actual block height on wallet creation, due to inaccurate approximation

Related issues:

• Wallet API: persist first refresh restore height set by daemon seraphis-migration/monero#130 (comment)
• Bug: start_height not being respected both in "refresh" RPC call and Wallet.cpp API. #9362 (comment)

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Changes made:

• Use latest hard fork block (src) for get_approximate_blockchain_height() (src).
• Update approximate_rolled_back_blocks (src) and also apply it for MAINNET.

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Some more info

Note: negative values for deviation mean the estimated height is higher than actual height.

Current estimates (starting from v2 height, offset by approximate_rolled_back_blocks, one month safety margin):

nettype	estimated	actual	deviation
mainnet	3498067	3517127	19060 (~ 26 days)
stagenet	1942002	1964485	22483 (~ 31 days)
testnet	2857971	2850082	-7889 (~-10 days)

Note: I included the following table just to show how bad the estimates would be without applying approximate_rolled_back_blocks. I'd argue it makes sense to apply it for MAINNET and to keep an eye on it when the hard forks get updated in the future. For the actual difference that this PR makes see Historical deviations below.

Updated estimates (starting from latest height in hardforks.cpp, without approximate_rolled_back_blocks, one month safety margin):

nettype	estimated	actual	deviation
mainnet	3532426	3520682	-11744 (~-16 days)
stagenet	1994540	1967959	-26581 (~-36 days)
testnet	2858138	2853760	-4378 (~ -6 days)

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Historical deviations

With help of a python script (search for NOTE to find adjustable parameters) I compared the historical deviations between actual - expected block height, starting from fork_block src until today in one month increments

With old rules (starting from v2 height, offset by approximate_rolled_back_blocks, one month safety margin):

nettype      min blocks days  max blocks days  avg blocks days
    mainnet      49152  ~ 68      52224  ~ 72      50530  ~ 70
   stagenet      21504  ~ 29      79456  ~110      47401  ~ 65
    testnet      -7268  ~-11     363520  ~504      89514  ~124

With new rules (starting from latest height in hardforks.cpp, with adjusted approximate_rolled_back_blocks, one month safety margin):

nettype      min blocks days  max blocks days  avg blocks days
   mainnet       22016  ~ 30      23040  ~ 32      22440  ~ 31
  stagenet       22272  ~ 30      44032  ~ 61      33261  ~ 46
   testnet       22528  ~ 31      48128  ~ 66      37644  ~ 52