fix: BondedTokens exceeds int64 range (#300)

## Description

Closes: #XXXX


fix bonded tokens / unbonded tokens exceeding range with int64. 
Store the value as string instead. 


---

### Author Checklist

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please add links to any relevant follow up issues.*

I have...

- [x] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [x] targeted the correct branch
- [ ] provided a link to the relevant issue or specification
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
- [x] reviewed "Files changed" and left comments if necessary
- [x] confirmed all CI checks have passed

### Reviewers Checklist

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I have...

- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

database/gov.go

@@ -341,7 +341,7 @@ ON CONFLICT ON CONSTRAINT unique_staking_pool_snapshot DO UPDATE SET
 WHERE proposal_staking_pool_snapshot.height <= excluded.height`
 
 	_, err := db.Sql.Exec(stmt,
-		snapshot.ProposalID, snapshot.Pool.BondedTokens.Int64(), snapshot.Pool.NotBondedTokens.Int64(), snapshot.Pool.Height)
+		snapshot.ProposalID, snapshot.Pool.BondedTokens.String(), snapshot.Pool.NotBondedTokens.String(), snapshot.Pool.Height)
 	if err != nil {
 		return fmt.Errorf("error while storing proposal staking pool snapshot: %s", err)
 	}

database/schema/03-staking.sql

@@ -14,8 +14,8 @@ CREATE INDEX staking_params_height_index ON staking_params (height);
 CREATE TABLE staking_pool
 (
     one_row_id        BOOLEAN NOT NULL DEFAULT TRUE PRIMARY KEY,
-    bonded_tokens     BIGINT  NOT NULL,
-    not_bonded_tokens BIGINT  NOT NULL,
+    bonded_tokens     TEXT    NOT NULL,
+    not_bonded_tokens TEXT    NOT NULL,
     height            BIGINT  NOT NULL,
     CHECK (one_row_id)
 );

database/schema/08-gov.sql

@@ -65,8 +65,8 @@ CREATE INDEX proposal_tally_result_height_index ON proposal_tally_result (height
 CREATE TABLE proposal_staking_pool_snapshot
 (
     proposal_id       INTEGER REFERENCES proposal (id) PRIMARY KEY,
-    bonded_tokens     BIGINT NOT NULL,
-    not_bonded_tokens BIGINT NOT NULL,
+    bonded_tokens     TEXT   NOT NULL,
+    not_bonded_tokens TEXT   NOT NULL,
     height            BIGINT NOT NULL,
     CONSTRAINT unique_staking_pool_snapshot UNIQUE (proposal_id)
 );