Update postcli for compatibility with multismeshing

[fasmat]

Part of https://github.com/spacemeshos/go-spacemesh/issues/5089

Closes #219

This updates postcli with the changes for multi-smeshing setup.

• postcli now stores a generated key in identity.key instead of key.bin and informs the user that they have to copy the file to the datadir of the node
• Added multiple checks to ensure users don't accidentally corrupt or delete their PoST data files:
  • the key in identities.key is checked to be compatible with the NodeID in the postdata_metadata.json file (only if both files are present
  • a provided -id is checked against both the identities.key file and NodeID in postdata_metadata.json and user has to confirm a warning that providing a mismatched value potentially corrupts their data.
  • -numUnits has to be set if postdata_metadata.json cannot be found. If postdata_metadata.json is present the value will be read from there. If the provided value does not match the value in the postdata_metadata.json file the user has to confirm that they want to continue and is informed that providing a lower value will delete data.
  • -commitmentAtxId has to be set if postdata_metadata.json cannot be found. If postdata_metadata.json is present the value will be read from there. If the provided value does not match the value in the postdata_metadata.json file the user has to confirm that they want to continue and is informed that providing a wrong value can corrupt their data.
  • provider has to be set
  • labelsPerUnit and scryptN trigger a warning if set and do not match mainnet values. User has to confirm that this will generate data that is not compatible with mainnet.
• All text that is printed now uses log.Print and log.Fatal instead of fmt.Println

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 38.46154% with 8 lines in your changes are missing coverage. Please review.

Project coverage is 74.3%. Comparing base (3cd36cc) to head (61f0fbc).

Files	Patch %	Lines
initialization/metadata.go	28.5%	5 Missing :warning:
initialization/diskstate.go	25.0%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #270 +/- ## ======================================= Coverage 74.3% 74.3% ======================================= Files 29 29 Lines 1539 1543 +4 ======================================= + Hits 1144 1147 +3 - Misses 254 258 +4 + Partials 141 138 -3 ```

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