chainHead: Ensure reasonable distance between leaf and finalized block (#3562)

This PR ensure that the distance between any leaf and the finalized
block is within a reasonable distance.

For a new subscription, the chainHead has to provide all blocks between
the leaves of the chain and the finalized block.
 When the distance between a leaf and the finalized block is large:
 - The tree route is costly to compute
 - We could deliver an unbounded number of blocks (potentially millions)
(For more details see
https://github.com/paritytech/polkadot-sdk/pull/3445#discussion_r1507210283)

The configuration of the ChainHead is extended with:
- suspend on lagging distance: When the distance between any leaf and
the finalized block is greater than this number, the subscriptions are
suspended for a given duration.
- All active subscriptions are terminated with the `Stop` event, all
blocks are unpinned and data discarded.
- For incoming subscriptions, until the suspended period expires the
subscriptions will immediately receive the `Stop` event.
    - Defaults to 128 blocks
- suspended duration: The amount of time for which subscriptions are
suspended
    - Defaults to 30 seconds
 
 
 cc @paritytech/subxt-team

---------

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>
Co-authored-by: Sebastian Kunert <skunert49@gmail.com>

Cargo.lock

@@ -2624,9 +2624,9 @@ dependencies = [
 
 [[package]]
 name = "clap-num"
-version = "1.1.1"
+version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0e063d263364859dc54fb064cedb7c122740cd4733644b14b176c097f51e8ab7"
+checksum = "488557e97528174edaa2ee268b23a809e0c598213a4bbcb4f34575a46fda147e"
 dependencies = [
  "num-traits",
 ]
@@ -2844,10 +2844,11 @@ checksum = "acbf1af155f9b9ef647e42cdc158db4b64a1b61f743629225fde6f3e0be2a7c7"
 
 [[package]]
 name = "colored"
-version = "2.1.0"
+version = "2.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cbf2150cce219b664a8a70df7a1f933836724b503f8a413af9365b4dcc4d90b8"
+checksum = "2674ec482fbc38012cf31e6c42ba0177b431a0cb6f15fe40efa5aab1bda516f6"
 dependencies = [
+ "is-terminal",
  "lazy_static",
  "windows-sys 0.48.0",
 ]