Fix staking counter

[ales-otf]

Description

• Fixes the issue, when the block of the last stake/unstake was reset to the current block.

• Removes get_stakes_this_interval_for_coldkey_hotkey and set_stakes_this_interval_for_coldkey_hotkey by
  replacing it with try_increase_staking_counter.

  For a getter, get_stakes_this_interval_for_coldkey_hotkey has an unwanted side effect of mutating the storage.

  set_stakes_this_interval_for_coldkey_hotkey is just a storage setter.

  Both methods used only in do_add_stake and do_remove_stake.

• Replaces StakeRateLimitExceeded and UnstakeRateLimitExceeded error variants with StakingRateLimitExceeded as we don't separate rate limit logic and value between staking/unstaking.

Related Issue(s)

• Closes Fix Stake rate limit for target>1 #1091

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please describe):

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have run cargo fmt and cargo clippy to ensure my code is formatted and linted correctly
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules